I saw this movie a while back not sure what the name is but I know a little bit that I can remember so here goes, this one guy is investigating something like a paranormal thing, his trainee is a young guy falls in love wit the girl in the house, there is this machine that opens a dimensional door and they see these jellyfish like things floating around later on in the movie the older doctor guy is going through the door and changing the apprentice guy is sucked in then dies? But comes back and is eating brains in the hospital they confront the doctor and he eats the head of his apprentice killing him then its like off nightmare on elm street when you see freddy coming out of the guy, the apprentice's brain I guess is attempting to take over the doctor and is forcing his way out of the doc's body oh and by this time the doc has mutated into this creature that has a third eye tentacle thing in the middle of his head, yea I know my description is horrible but I'm trying to remember a movie I saw once years ago

Sounds like From Beyond from 1986.

I don't know its been so long I don't remember any names or anything like that

I can't rate the answer above at the moment, but I agree with it 100%. It's From Beyond, without a doubt.

You I found the from beyond synopsis on wiki and checked it out it is that movie so I'm happy to have found another movie I been trying to find for years