I Need Help!

Hello friends. Recently, I make a gaming pc; because I love to play Grand Theft Auto on pc. Whenever I start a game on pc, 95% of my computer's CPU is being used. But GPU is being used only 15%. Guys, I don't understand why this is happening, and how to fix this issue. Can anyone help me with this? Any help will be appreciated.
PC configuration:
CPU – Ryzen 5 3600
Motherboard – AsRock B450M Steel Legend
Memory – Adata XPG D30 8GBx2 3000Mhz
Graphics Card – Zotac Gaming GeForce RTX 2060…

I Need Help!