minecraft isint opening

so when ever I tried opening Minecraft java edition 1.16.4 it kept crashing and saying (not responding) and also the screens fades a little to white. so anyways it gives me an option towait for it to respond and to just close it. I tried to wait so i waited for about 4 hours and it didn't work. But with 1.8 Minecraft  it opens it shows the main menu but it didn't load the world it just said "generating world" I think so is it a Minecraft bug or just to do with my windows pc?