Trouble with nether

So on mobile Minecraft (pocket edition), I was having trouble with entering the nether. I don’t know if it had to do with me being at a low y level, but blocks are turning invisible, I cannot exit the nether, and I cannot access the menu. Each time entering the nether, a new nether portal was created. This stopped after three appeared. I have tried restarting the app and my phone, but nothing has changed. *Update I have tried this on another world, and the portal worked, I could go in the nether and break blocks, but re-entering the portal brought me to an entirely new location. It’s the same with the first in a super flat world.