im sorry but all of you are wrong*, dm is not a good place to point a new player in a situation like this.
good dm is just as much about confidence as it is about practice. going negative and getting shot in the back constantly for hours in dm is going to not only turn him off competitive but the practice hes going to get is going to be minimal at best.
start off by playing mge with people your level or a bit higher and play different classes and maps but mainly scout and badlands mid. play pugs and scrims and just a whole lot of scout in general. find a comfortable sensitivity and stick with it, dont keep changing your setup or config.
its kinda strange how every thread like this people who dont have good dm or ever had good dm post "play dm" "practice" "play the game".
add me on steam i think i could help you out on your scout nixstarax.
*i agree with your post loljk