Kevinorf

Codreanu meant the To Berlin campaign, played from the Soviet side... Any tips on that one?

Yes, it takes a little practice but especially with the US 60mm mortar and also the 81mm you get a semi-indirect fire effect from a defilade position. That means you position your mortar just behind a ridge. That way only other artillery will be able to get you. This mission had two purposes I wanted the Germans to reveal some of their position. Be aware do always combined arms. With a human player it is not that easy but the AI is pretty dumb. Yes, for proper indirect fire your mortars need a radio nearby. Another reason to use the direct fire mode by carefully selecting the terrain. Your ammo is soon wasted by spotting rounds.

This is a common experience my friend.  I started with somewhat larger scenarios in RT (because I like a lot of armour and possibly because the demo scenarios were I think medium size) and soon found I had pre-conceptions of what my heavy panzers could do.  I was on a steep learning curve and had little idea of how to manage movement, comms and LOS/LOF.  I'm still learning and sometimes (particularly against PBEM players) you just have to accept that the mix of game setting, units etc. combined with your own capability and luck have not worked out in your favour.  The opponent's capability might also come into it 😉.
I'm not sure about practice scenarios but will have a think.

While smaller scenarios would seem to be better for learning, conversely in the smaller scenarios a very few casualties can mean a loss.  The advantage of large scenarios is that (usually) one can take losses and learn from that, but still have reserves to move forwards with one's (hopefully improved) plan.

Sometimes the bigger ones are better as they force you to take your time, or at least should.
Take your time with the game. No need to hurry through. Look over the battlefield, get down to ground level to get a good idea of the terrain and plan your moves. It takes time and practice, usually lots of both...😀

In FB Trouble with Siegfried and a Muddy Affair. 

Advance on the right slowly use your engineers to clear a path through the minefield. Create a base of fire on the right side of the map then you push left. Capture I think the hotel there. Minefields are created to funnel your approach in a killing area of your opponent's choosing. Always consider attacking a minefield. 
 

The very best CMFB scenario that I recall as the best was "Mission to Maas".  However, it's VERY big and you'll need a powerful machine.
Other than that in terms of training you may not want to play the very best scenarios as that may "ruin" em for you.  So, maybe learn on lesser ones until you fancy yourself to be a good player.  So, for starters, you could just pick any scenario from the list that tells you it's big.
 

A War Without Mercy. You need to do research and learn tactics. If you play it seriously this game can take up to a year. Study the terrain, organize your traffic and formations. I would say look at it six months from now. 

While I agree this is an excellent scenario, I would definitely not recommend it for a beginner.
However, the same author made a whole campaign for KG Peiper, called "Rollbahn D".
It's an enormous campaign, but the first several battles are quite small and not too difficult, since they are in the beginning of the attack when the Germans had the advantage.

The Allied campaign in FB looks pretty interesting too. I might give that a go...

Sadly, both "Outlaws" and "Montebourg" feature fictional PzIVs. But, if you're OK with that them give them a go.
As previously mentioned, both "Devils Descent" and "Blunting the Spear" are excellent. Once you've played them you might be ready for "Rollbahn D" the best ever CMx2 campaign.

Road to Nijmegen is buggy reason I didn't complete it apart from the first two games I won't waste my time on it. Just play Bridge No7, Nijmegen Road Bridge and Back over the Waal scenarios. These scenarios should have been in the Campaign. 

Devil's Descent -- Pitch perfect company sized para campaign.
Kampfgruppe Engel (CMBN) -- Not a beginner level campaign, but one of the most innovative in Combat Mission. Features ammo and repair state carry-over and core force.
The Outllaws (CMBN) -- Ramping para campaign, where you start small as the troopers march to the sound of the guns, culminating in much larger battles as your paras link up with 4th Division straightlegs coming off the beach. Interesting briefing style that provides virtually no useful tactical information. but it does provide a narrative, and the player fills in the blanks.
Road to Montebourg (CMBN) -- One of the most ambitious Combat Mission campaigns, and one of the biggest (16 missions?). Excellent mission variety, with the opening mission a showcase for suppression in Combat Mission.
Blunting the Spear (CMRT) -- Battalion + sized campaign. I tend to steer clear of the larger campaigns, but this one is too good to ignore. A near perfect blend of long range gunnery duels and close-in fighting.
Just a few suggestions

CMBN The Road to Montebourg is a classic. It’s long but it has a bit of everything and there are plenty of playthrough videos on YouTube if you want some tips

I think my first WW2 campaign was the KG Peiper one from FB, which was challenging but a lot of fun.  Whether this counts as 'smaller and easier' I'm not sure.

I dismount one terrain feature away. Yes, I always grab the Javelin. The thermal sights are even useful after you fire the missile. Also you can use it as a precision munition but it is an expensive one. But if it saves a highly trained specialist, it is worth it. 

Ohh!  And for the main attack.  Use smoke to cover!  I actually moved the Strykers with long guns up onto the berm and then had 2 or 3 Abrams roll in with my Strykers and infantry. Infantry dismounted in the fort, there was a very brief firefight with tanks, Strykers and infantry all unloading and boom, the Syrians surrendered with only a few minutes left.
And another thing....  As MMM said, always take your javelins.  They are great for spotting on top of killing tanks and have one of the best optic systems available with huge zoom.  Your javelin teams, laying low patiently, WILL spot tons of things.  Cover arcs are your friends too as you can set up OPs, set a cover arc and your men won't fire and expose themselves.
You will learn quickly, how important it is to sometimes just sit and spot for minutes on end.  
 

Great replies. Thanks all!

Patience.  Patience above all else.  This is one of the biggest stumbling blocks for new players, imho.  
I think I spent 75% of that battle with my Abrams on the berm and my FOs calling in fires etc. for all that time.  You don't need to press and you just have to wait for your arty and tanks to do their jobs.  Let the Abrams sit on the berm and systematically take out everything.  You don't even need your MG teams out on the berm as the range is getting a bit long there and they would just be wasting ammo.  Stay at range where you can deal all your damage and they can't touch you!  You have thermals and night vision!  Huge advantage.  Stay back and dismantle them at a distance where they can't do a thing to you.  PS, those old dug in Syrian tanks can't hurt your Abrams.  Sit back and pick em off one by one.
At about 15 min left, I called in all my heavy artillery on the barracks and fortress.  Call linear strikes across the buildings, the heavy arty will level those buildings or cause massive damage to the building and those inside. Once those start hitting and kicking up dust etc. that was the time to move my Strykers in.  I dismount my infantry about 300-350m from the the enemy lines and they pretty much just mopped up with Stryker support.  My artillery pretty much leveled the fortress and the enemy surrendered about the time I rolled into the smoking fortress.  I think I only lost 2-3 men and maybe one Stryker at well trying to get through the mines.
The biggest hurdle will be for you determining how to utilize your infantry, set up attacks and determining when to launch.  Patience really is everything in learning how to watch things develop and then time your attack at the opportune moment.  A lot of CM battles will be very low key and not much combat as you maneuver, scout and work yourself into your attack positions.  Combat tends to be, and should be, extremely violent, fast and furious.  With all the American firepower, USE IT!!  Annihilate everything and when your enemy is back on his heels deliver the killing blow.  The big fights tend to only last a couple minutes.  When things get drawn out is when you get in trouble.  I suggest really paying attention to effective ranges and knowing when and where and how to use your different weapon systems.  Infantry should only be dismounted and engaging close up or otherwise used in small scout teams, or with javelins to sit way back and just spot.
You are the Americans, overwhelming firepower and destruction is your friend.  Use it all.

Smoke once you breach the minefield. You can see right through the smoke with your thermals. 
 

When I played this the Abrams were parked on the berm and didn't move (hull-down of course) and provided supporting fires on identified targets. I took one platoon DISMOUNTED with their Strykers and moved them through the mines once the engineers had marked them. There is still a risk that the mines could go off and IIRC I did lose a Stryker driving through the marked minefield so best to get your guys out.
With that platoon I inched SLOWLY towards the compound and if they were engaged then use the supporting assets to blast the snot out of them. All the while the FO was up on the berm calling in indirect on the building at the front at first and once they were demolished/cleared then roll the barrage on through the compound.
The other two platoons: I had one dismount and run over the berm (yes they can make it over) and set up a base of fire and the other was held in reserve. I didn't need them in the end as the AI surrendered. I can't remember how may casualties I had but it was single figures, and two of them were taken out by mortars.
Always best to grab Javelins if they are available.
MMM