At first, the game doesn't look hard, but the more you will play it you will learn quickly that the needs a lot more skill than you thought, and that's when the questions start being asked: "how to get better".
Communication in the game is very important because it can save you or your teammate. First, you will have to learn the names of which positions the enemies are in. You will have to have a good sense which essentially means that you will have that feeling when the enemy will make a move or when will he rotate and what is he gonna do next.
In-game you will have to practice pre aiming some corners in which usually enemies are, which means that if an enemy will every round go to the same place you will start positioning your crosshair where he was every round and that will help you get more kills.
If your gonna play bad some matches start thinking about what you did wrong or right previously and with the info you will gather from that you will start to improve your skills and game sense.
Which guns you should buy in-game if your playing as a counter-terrorist, in a pistol round just play with the usp-s and try to get headshots. If you lose the first round don't worry because you can go eco the second round and a full buy the third one. Full buy means that you will buy grenades, armor, and guns. If you see that an enemy player will camp you with the AWP play differently and start thinking about ways that you can trick him and in the end kill him as well.
Ranks: Silver one, two, three, four, and elite, those are the ranks where players start learning about the game callouts and which guns to use. After silver comes gold nova one, two, three, and master in these ranks there are players with quite a medium amount of hours in-game which essentially means that they know mostly everything in the game. From that, the ranks get harder and harder to get, the players that play in the top ranks are usually one of the best in the game and they mostly have over 2000 hours in-game.
I hope it will help you and give you an advantage over your teammates or enemies.