@im19825 Great, if you've got all the DLCs then I'd recommend unlocking the Federovs for the medic class, if you haven't already. They're basically assault rifles so you can hold your own quite well up close, but still be effective at range by using single shot or bursts. I am biased there slightly, though, as I have 100 service stars on the Optical version, so used it a lot. The Cei-Rigotti, Autoloading Extended, M1907 SL Sweeper are all very decent IMHO too.
If it helps, I mostly use the BARs for Support as I find them effective at short to mid range (you'll reload a lot though), or the IMG from the Tsar DLC since it has a high ROF. I also generally use the Lee Enfield variants (or occasionally the M.95 carbine) for Scout as the sweet-spot is decent...and I'm British lol. I don't play Assault much, but when I do I usually favour the Ribeyrolles from the French DLC to give myself some range.
Positioning is key in Battlefield, but you should pick that up naturally as you learn the maps. Although, it might be worth sticking with your team as much as possible and focusing on supporting roles (spotting, healing/reviving, and resupplying) over kills should help you learn how to play the classes effectively.