i was thinking of ways we can help each other with this game, there's always room for improvement or a little tip that can help get that achievement that you wanna go for.
DONT FORGET TO LEAN, this thing can help you keep from getting hit in the lower half, which can be a lot more deadly then it seems.
the Alt button is sneak walk (read as: burger king man). This can prevent an enemy from hearing you. As someone that wears 7.1 headphones, this can mean life or death.
Sprinting is great but you shouldn't turn corners before checking either your map (LETTER N....... or tab) to check for friendlies, or peeking around for enemies. Also, reference to the previous point. The sprint and tab combo equal default steam overlay mix-up
Borderless windowed can help transition between desktop and the game easier. Before doing this i found once in a while the game would not bring the visuals back up but the game was running as normal.
To get a good grip on your enemies' tactics and routes, I would recommend playing as every team, at least 5 games. You will get to see your cover from the enemies' eyes and look for spots that are actually awful for providing cover.
Get a german grenade skin mod, this thing makes your life a whole lot easier. It will give a visual colour reference to determine if its a smoke or frag.
For tracking a flamer, you can get a scorch mod so it gives clear burn tracks. Once in a while you gotta hunt a bear.
Practice mode can help you learn the Leader role pretty well. Helps the transition
If you are going for Headshot achievements, i would recommend using a sniper role when available. Even if you don't use a scope, the role gives you the advantage of holding your breath longer.
For the Bayonet or Melee achievements i would suggest Dunkirk for Allies or Breville as Germans and to try a heavy kit with smoke grenades. You can make a smoke room and move around relatively freely. The assault role gives you faster movement as their upgrade, so this can help you either run to or away from a combat situation. The rifleman class gives you more stamina, so this can also be a good option.