Premiere Pro Keeps Pin Wheeling freezing

I just got my Mac back from being repaired. Before I sent it in I was having an issue with it constantly freezing every time I did something in my project but eventually it would unfreeze long enough for me to add something else in my project. When I finally got done with it, it wouldn't let me export so I tried a software update which made my computer refuse to take me back to my Home Screen. I called apple to find out my computer hardrive had to replaced.

Anyways a week and a half later.

My hardrive & flash was replaced and I got my computer back yesterday with nothing on it. I reinstalled premiere pro. I opened my project and it won't let me click anything without feeezing. It's even worse than before. I have a huge project that should've been ready weeks ago. Someone said to go to file and general to set the renderer to software only but after 30 minutes I couldn't even press file or anything else at the top of the page. When I finally got there it already is under software only. 

Update: As I have written this, it is finally letting me click things but It still freezes after a while and then lets me move around again. What should I do? I don't want this to keep happening.