Question How do I fix my computer from being extremely choppy

[HumanPerson]

I accidently hit the back of my gpu when the computer was running and since then, the computer has been very choppy. I've had this rig for about 4 years so the performance was slowly going down but after this it has probably gotten 10x worse then it was.I cant really run many games so I would like to know if its possible to fix the gpu or do i just need a new one.It just seems it cant handle games or more than 1 twitch stream.

I have a gtx 970 and an i5-4690k.(has stock cooler)
Also, one of my case fans dont work.
8gb of ram

 

[rgd1101]

make and model of the psu?
check cpu/gpu temp?

 

[HumanPerson]

Last time I checked, the cpu would be around 50-70 without much stuff on.(probably 3 weeks ago.)
I was just running youtube and it was hitting 90 and its about high 60s at rest (just now)

the psu is the evga supernova 750b 80+ bronze

the gpu is at 50

 

[rgd1101]

cpu is overheating. redo the thermal paste

 

[HumanPerson]

Should I just get a new cpu fan since I probably need it and I dont have any thermal paste? Also, The problem occured when i tried to unplug the case fan and that was when i hit the gpu. So the cause of this random drop is due to me either unplugging it or damaging the gpu.