iMac mini tv display issues

Hi everyone.

I've been trying to change the display settings of my iMac mini, because I couldn't see the top bar on the screen.

But now I have another problem; my tv doesn't support certain display format. It specifically says: this tv doesn't support the output format, video resolution and/or refresh rate being sent by.... etc, etc.

The thing is that now, I don't know how to fix this, because the computer won't let me asjust it.

Please help!