pip3 backend dependencies failling

[DekStef]

I am trying to install matplotlib using pip3 install matplotlib.
It always fails when the backend dependencies start to be downloaded.

After that, it always gives me:

So i tried to install cmake using pip3 install cmake. It also fails. After, i tried to isntall ninja. and it always gives the same error that is connected with the backend dependencies.

I already updated pip and I also tried to use an older version 58.0.0. Nothing seems to work. Please help me.