Question PC Runs Way Slower Than it Should..

[Valelul]

3 Years ago i made a mistake buying a ready builded PC by Medion.. Everything was perfect, everything runs very good, no errors, no framedrop. In a day didn t want to start anymore. Like i pressed start button, starts for 1 sec and then goes off... I dont know if that s energy loss or something, if it would i wouldn t know from which component that might be.. I send it back at repair because of warranty. Came back a little slower, when i started it from start button, would take more than 5 sec to reach desktop, which first time needed only 3 sec to reach desktop.. This time after 1 month had the energy loss again.. i mean just doesnt want to start anymore and i have to take the cables out and back in many times before opening again..(as it happens now too, even when i let it on sleep) First i tought it s the PSU that s too weak for the other Components.. Send it 2nd time to warrranty, and this time i got it back worse than it ever was... Games not running over 60fps.. frame-drops, can t watch a youtube video thats 1080 60fps(Before 2nd time could watch almost everything in 4k 60fps), and when i ll start it, i had to wait much longer now to reach desktop and also got a msi picture on screen that allows me to enter bios or boot. I think they changed the bios version, GPU and MOBO were changed bcs they burnt or something like this they said. Now.. as i said, first i tought that the PSU is too weak, but it doesn t explain why even c.s 1.6 doesnt run at optimal fps.. played for example one old game Reksio and when i used spells on many birds they would freeze from the speel as they get more it just runs like in 3-5 fps... Any help is welcomed. Thank you.
I also think about some cpu errors bcs gpu doesnt seem to change very very much of the fps when lowering setttings in games, some lowering settings even might lower fps too in some games xD so idk..

OS: Windows 10
CPU: Intel i7 4790
MOBO: MSI Z97 Gaming 7
RAM: 16 GB 1600mhz DDR3
GPU: Nvidia GeForce Titan X 12GB
HDD: Some WD 1TB (D+E = 900 GB)
SSD: Crucial 25(so its written on it) C has 237 gb tho
PSU: Cougar 700W BronzePlus

Btw: sorry if it should ve been posted somewhere else , i dont know the forum and tought Components it s allright xD

 

[rgd1101]

cpu/gpu temp and usage during the game?
ran/ssd/hdd usage during the game?
malware scan the system?

 

[Valelul]

Temp i dont know exactly, i ll download a program for it right away, all tho i think cpu goes somewhere beetween 60-65 maximum in gameplay bcs i looked at coolpaste and it s almost completly dry after 2 years.
Didnt found no malware yet, but how could it be from malware because they just send it back when opened again i think..
For example now have league of legends opened and 5 tabs in google chrome opened:
In App Manager shows me cpu (between 2-5%), memory (have 21 without change%), disc (which i think it s the hdd ?.? 0%) network and gpu(most of time with these opened 0, but goes up to 10-32% maximum for a sec) dont know if it should show ssd too xD never had before.

 

[rgd1101]

looked at coolpaste

did you replace the thermal paste after you looked at it?

 

[Valelul]

I checked it yesterday but have none at home. So no, i ll buy me a good one these days. i mention that i didn t cleaned it, wanted to wait until i get a paste.
And you should look back at last responds bcs i may add usefull infos.
I also read on geforce.com that titan x recommanded psu would be 600W, so the 100 more would be enough for processor mobo and rams ?