This clearly is a hardware issue, either an insufficient PSU, insufficient cooling, or a graphic card that's not perfect anymore.
Your choice what to replace first.
when i play games on higher fps pc chrashes, screen on monitor becomes coloured (sometimes green,purple or just blank screen) and i hear fans or something a little bit luder (zzzzzzz) and it dont stop until i completly shut down pc, i dont hear any sound or anything from game i played so its completly freez or something with coloured or blank screen. For example when i play league of legends on best settings or cod warzone nothing happens but when i play PUBG or fortnite my pc chrashes but only if i play with uncapped fps, so when i play with capped fps pc dont chrash.Temperature is ok i even added some fans from old pc-s.
gtx 950, 12gb ddr3, i7-2600, hp 8300 is case and motherboard from it.
pc repairer changed thermal paste on processor and graphic card, he say is something wrong with graphic card like graphic chip or something like that but i want second opinion. If something is wrong with graphic card then how can i play same games on low fps and not on high? I heard that you can "fix" gpu by putting it in oven few minutes but i dont want to try that
yet.

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