My pc beeps and doesn't come on. Can someone help me find the problem?

First I set up my pc normally and then downloaded minecraft and steam and then suddenly it was black screen

And then he just kept walking and I switched it off and then switched it on again everything it does now is to beep 1 long and 2 short beeps all the time, see below and the ventilation goes on, yes and that's all. I just wanted to say one thing, I only got the pc today

Supplement after 3 hours

I still have one more question: How do I know if the graphics card is in it correctly, I have a geforce nividia rtx 2060

I have one more question, although the graphics card or something else is incorrectly placed in the picture, someone can see a reason why it beeps in the picture

*see below

https://de.wikipedia.org/...lt%C3%B6ne