meaningless game grinding

After playing two games, the game suddenly starts to lag and becomes unplayable, even though there were no issues before. When the game first came out, I didn't have this problem. I really spent a lot of money on it, but I feel cheated. I hope there is a solution. I am listing my computer system below.

Processor: AMD Ryzen 5 5600H
RAM: 16GB
Graphics Card: RTX 3050