Making round buildings can be suprisingly hard in Minecraft. Luckily there are some tools to help you on this issue.
One of the most common ways to improve your CS:GO skills, is to change the crosshair in game. It can make you more accurate and improve your aim significantly.
Using the default inventory in Minecraft can be a bit limiting at times. The UI could be faster to use and of course, you could have more space in there.