Well the advice i can give you is to keep playing, only hours will make you better! Dont focus to hard on aim, movement and crosshair placement are propably the 2 most important things when it comes to shooting.
When do i peek, how do i peek, how do i make it easy for me to hit the shots but hatd for the opponents, is it it a right eyed/left eyed peek, so i wideswing, jiggle etc. Is the opponent low so i aim for body or is there maybe an awpwr that i cant just peek. There are many things you just gotta get a feel for and you dont really get that feel in dm.
I would suggest u just try around a bit with the sense and when u think u found one just stick with it. Dont change ur settings all the time and get comfortable with ur settings and setup. Ofc u can play some dm or aimbotz as well but sont be too harsh on yourself, its all a learning experience and it will take thousands of hours to learn all this things and get them down almost perfectly:)