Game gets laggier as I play

I play on PC, my specs are GTX1650, i5-10500H, 16GB ram and the game is on the SSD. Temperatures are always below 80 when gaming.

The game works perfectly fine for me when I start it up. But it gets laggier the more I play and after about 30 mins of gameplay the lag becomes quite noticeable. I know for a fact it isn't thermal throttling. Why is this happening and does anyone know a fix for this

Yes my specs are quite outdated but the game runs fine on low-medium for some time. But it starts losing fps like crazy as I play