tekin1963

I have a Mercedes C-180. There is a problem with my navigator-radio system. Sinds two weeks it is saying insert navigation CD and has a problem with reading it. I do not want to use the navigation anymore but only listen to radio. It is not coming further than please insert navigation cd and cd fehler. So my question is: How can I start my radio and turn off navigation? Or how can I use my radio. I pressed a lot of buttons and tried everything. It came twice back and I could have started the radio. But then it went back to navigation. And now I cant even get it back for a while. Any help will be appriciated. I uploaded also 2 pictures of it.