Do you think osu really help with your aim in games like Minecraft, CSGO and more?

Osu definitely helps with reflexes and reaction times but not so much aiming. If you want to practice your aim for CS:GO you should check out "Aim hero" on steam. It has sensitivity options for a lot of esports games which allows you to sync your aim between them. As a person who is quite good at Siege I find it very helpful.