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 ♠]

-Yeah hairworks are huge hit to fps, but I want fluffy animals so I will keep it I have only shadows on low ( no visual difference ) and foliage on high, everything else maxed with ALMOST solid 60fps. I overclocked it to try if I will be able to have solid 60fps, but nvm.. the game is optimalized very well and 50-60fps is butter smooth for me.
- Not only Hairworks are huge hit to fps, turning shadows from low to ultra takes like -7fps and foliage from high to ultra -15fps ( yeah lol just for few more bushes in background).
Thanks for answers