Well it takes endless till it opens a small project with only a 3minutes mp4 (video and audio) and very few graphics and transitions in it (about 10-15 minutes?). (Before this problem occured it opened it within seconds... )
When you click on something to edit ... like a graphic or audio... nothing happens... or again you have to wait for several minutes... when you click on "effects" nothing happens...
BUT there is not the "not responding" message... that message only appears when you click too often.
Now I can tell for sure it's not caused by gtx 960m. Check if you have enough free space on the C: drive and Premiere Pro cache drive. If that is not the case, something is likely wrong with your OS, like a virus, or 3rd party tool that eats all resources (like antivirus, lol), or maybe faulty HDD. Try to close all background apps while running Premiere, plus check windows task manager for CPU/HDD/RAM utilization. That should give some hints what is going on.