(My native language isn't english, sorry if I want a mistake)

When I play (for instance Ark:Survival Evolve) the game go 60FPS, and suddenly go 15FPS, I have GPU and FPS picks, look at the screenshots with MSI AFTERBURNER. I need a solution or recommendations (My gpu is RX 480 4GB)

PS: My pc is new, it have 3 or 4 days

Picos FPS.jpg
Picos GPU.jpg