MacBook Pro problem with screen freeze My MacBook Pro 13" mid 2012 worked perfectly, but last days it has many lags (screen freeze with or without artifacts/shaders). After force shutdown it beeps 3 times and after approximately 10 minutes it loads OS, but fan works very noisy and fast.

Where can be the problem?
I have a Macbook air mid 2012 and it still runs like it is brand new. If I were you, I would get an external, backup everything you have on there. Do an internet recovery through disk utility and it should run like its brand new! Ive had issues like this before and what I suggested has been successful for me every time.