Overclocking CPU, I need an advice Options

[♠ The Joker ♠]

My rig:
CPU: intel i5-2500k Quad Core 3,30 Ghz
GPU: Msi Gtx 970 Gaming 4GB
RAM: 8GB
OS: Windows 10 Home
Monitor: 1920x1080

Hello, I have done my 1st cpu overclock and the results were not according to my expectations. I overclocked 33 CPU Ratio to 40 so each core has 4,0 Ghz and CPU Core Voltage to 1150 V. I tried playing Witcher 3 Wild Hunt afterwards and there was 0 difference in performance, FPS was the same only CPU temperature raised from 38-50°C (60°C+ while gaming) to 70°C+ after few minutes, so I turned CPU settings back to normal. I don't know if the problem is that my CPU is 5year old ( it's the only part in my pc that I haven't upgraded yet) and the thermal paste must be completely decomposed and that I am using CPU stock cooler, but other people who I know got a lot better results. Can you guys please tell me what's wrong or advice me what settings should I use? I am 18 years old and studying at Grammar school so I am not so good at those things, actually I am noob
I am looking forward to your answers. Thanks
( Sorry for my english)

[♠ The Joker ♠]

Thanks for all the posts
- Obi, 970 is a bit better than 780. In Witcher 3, 970 beats even 780ti because the game was mainly designed for Maxwell (9xx) gpu users and 900 series gpus also render tesselation 3x faster than Kepler (7xx) gpus. But that's just only in Witcher, normally 780ti is slightly better, but not the 780 (sorry Trout )