How do I get the thing back together (power is currently off) or at least how do I get it that there's no danger when I turn off the power?

Turn it on again.

that was for the television.

Or for the reception of normal channels, but has become superfluous because there

Netflix, Youtube and Co.

Or for the reception of normal channels, but has become superfluous

The thing has absolutely nothing to do with reception, it's a plug.

What does the socket look like, in which this plug was inserted?

I took a photo and added it

The socket is OK. Can you turn the power back on. It is best not to reinstall the connector and buy a new connector strip.

This plug was for something else.

i needed the socket for my things, that's why i dismantled it.

that I have space.

the thing was full previous owner.

Why do you disassemble it so blindly and not take a picture as it was together. If you have no idea about electrical engineering, let an electrician do it or buy a new socket strip.