Do casual( silver -coated ) mirrors reflect radio waves ? If yes,tell me more precisely about the spectrum of wich they eventually can reflect radioelectromagneticwaves,if no please explain me why ?

What has your research shown?

This is a question you need to answer and we can help you from there.

In general silver does indeed relect long wavelengths such as radio waves, but practically speaking you would need a very large mirror to efficiently reflect or concentrate radio waves.