Gta 5 badly lagging in Nitro 5 an515-43 gtx 1650

But this game lags at even default preset at every turn every crash every sprint. Is the gpu/cpu underperforming or is the settings of gpu unoptimised? Also i noticed while cpu use reaches 90%, ram goes around 85-96% and gpu 50%. Checking frames, the game starts at 60 fps but then drops often even to 15 fps and even hangs when just looking around. Don't know what this thing's falling short of.