don't arms race (that's just fun). Do deathmatch. I always do at least 2 rounds of deathmatch before i go competitive. Play only main weapons: awp, m4a1s/ak47 with default pistols.
also i would recommend playing deathmatch with no sound or as little as possible. I use deathmatch only for aim/reflex. If you want to understand tactics and crap like that watch some BO5 of CS 1.6 and try to understand as much as possible. CSGO only became very tactical not so long ago.
I played 1.6 a very long time before csgo and a lot of competitive (like 1 summer 6 hours a day easy only 5v5s), that helped me understand where you should attack/hold, and where these places fit you best(try and test multiple places during game, and apply the best).
Because now you can find very easy vods and stuff like that looking at 1-2 players how and where they hold/attack sites would probably help you fast.
don't lose hope, and try to not get frustrated(impossible i know, i went ham on a kid on Sunday). Try your best, practice makes you better.
Also what I found out about myself, i need breaks, as in after 2-3 months of playing, if I take 1-2 weeks in which i don't play at all, i raise my level a
