Why can I only get 3 hours of sleep?

Can someone help me with so I got to sleep at like 10 or 11 and then I wake up at 2-3 and I can’t go back to sleep, I need sleep because I workout a lot and I’m trying to build muscle and I need to memorize a lot of thing that will go into my long term memory, so can someone help me please, it mostly that I wake up at 3 and can’t go back to sleep