I know it's kind of boring, but seriously do aim maps. I wish I had known about them earlier, would have saved me so much frustration. A few days of an hour or so a day of aim training is the equivalent of a month of getting **** on as a new player.
Game sense and getting comfortable on maps is a lot easier to pick up when you're not getting blasted right away and then sitting around dead for the majority of your playtime.
Aim maps? I didn't even know they were a thing. Are they just telling you where to point on a map for where people pop out or something?
Hit the subscribe button on this map:
https://steamcommunity.com/sharedfiles/filedetails/?id=213240871 and then watch the video on that page that explains how to get into the map and the different options available.
It's basically just target practice with any weapon you choose. There are others that have bots in them, which is a little more realistic as far as aiming for headshots and such, but I think this one is a good starting point. The spray control mode is good, but at first I would just focus on the regular quick-aim modes. There are better ways to practice spray control.
You really just want to get good with the M4 and AK... Unless you want to be an AWPer, in which case this map is pretty useless =p
There are a lot of other maps that do all kinds of things. Some of them are like what you mentioned, where it will teach you how to peek specific spots on certain maps. Dig through the workshop and see what you find. Mixing up training maps and comp matches with friends is the fastest way to improve, IMO.
There are probably even better maps than this these days, I stopped playing for over a year and am just getting back into it. So I'm not sure what else has come out, but I'm sure this will still be helpful.
