Path Tracing too noisy

Hello friends

I am trying to render this scene in path tracing, but the image is very noisy, even after a while it does not improve more than that mainly on metallic objects. Does anyone have any idea what I can do to improve? I just need a static render, not for real time

And another thing, whenever I take a high quality screen shot, the image is back on the start render again.

Thank’s and God bless you all!