with the given info we can literally say nothing...
what HW, Windows version, Driver version etc?
but try this:
go to powerplan and set switchable GPU on plugged in to "maximize performance"
than go to Windows Graphic settings and set Minecraft to "High Performance" GPU
PC: R7 2700X @PBO + RX 580 4G (1500MHz/2000MHz CL16) + 32G DDR4-3200CL14 + 144hz 1ms FS P + 75hz 1ms FS
Laptop: R5 2500U @30W + RX 560X (1400MHz/1500MHz) + 16G DDR4-2400CL16 + 120Hz 3ms FS