I am pretty bad at CSGO. So.., I'm seeking help here.  

same  

Don't move while shooting a rifle such as an AK, M4, FAMAS, etc... your accuracy is much lower while moving and it makes your shots miss

With rifles such as the m4, ak, there is recoil that makes your shots go higher than the crosshair after your first few shots:

To counteract this, shoot 1 bullet at a time against distant targets, and burst(3-4 shots) against mid range targets. For close targets, spray them, but crouch after your first few shoots to counteract the recoil.

Don't peek people with AWPs if you can avoid it, try to force them to rush you.  

And play death match a lot. And work your way up


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My favorite source on this topic: How to Practice CS:GO
I'd add that nowadays you can download maps like training_aim_csgo from the Steam workshop and I've found them useful for practicing specific movements.
Also, helpful console commands and such: Practice Configuration & Binds for Local Server

Some newbs look at the ground when running about. Instead keep your crosshair where your enemy's head might be so you don't have to move it as much when you see someone. More here: CSGO Crosshair Placement Tutorial  

Use google for once

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play lotsa pubs
mouse acceleration off
play more pubs
practice spray pattern
keep playing pubs
more practice
dont stop playin

general tips since early 2000s  

Toy around with your settings.

Find the perfect sensitivity for you.

Play in Casual or Deathmatch a lot.

Bet all your money on skins.

Pretty easy.  

learn to speak russian  

there are some really good training maps on the steam workshop that can help a lot, but in the end just play the game (DM, Comp, etc.) and over time you will get better!  

Learn how to peek/sidestep properly and your spray control, c9 n0thing has great vids on both which really helped me improve my game