Gaming pc doesn't work well despite great benchmark tests what to do?

I got myself a gaming PC three months ago with an RTX 2060 super and a Ryzen7 3700x with 2 times 8gb ram with 4000 mhz an ssd with 512 and a 1 tb hard drive I tried everything test so without end of benchmark test that showed that my PC works smoothly but the gaming experience speaks a completely different language. I mainly play fortnite and all my friends all have a super smooth picture and it jerks without end for me. I made the graphics card settings, made Windows settings or tried them out and have now restarted Windows completely So everything reset, I don't know what to do now. My colleague just had an idea that a cable in the PC somehow has a problem or it is simply defective and therefore my PC can't call up what it actually could because the benchmark test say that my graphics card is great and everything harmonizes perfectly with the broken cable is an opt ion or not? Would be so happy for an answer because I'm finished and have no more ideas at all

The utilization of your components would be good to know in order to be able to analyze something

What to do if you haven't already:

Update Graphics Drivers (on NVIDIA Homepage)

Activate maximum performance in the settings

Increase RAM speed in the BIOS of your mainboard

Unfortunately, I've already done everything 😅 but thank you anyway

Yes everything is idling that is the problem the only possibility would be overclocking right? -----> while I play fortnite cpu to 30% and gpu to 40%

Take a look in the Fortnite settings, because if your parts are not used to capacity anyway, overclocking will not do you any good either

I play performance mode with low textures