The end-of-map vote should be enabled by default. The vote will come up approximately 2 minutes before the end of the map (assuming the map is set to end at all i.e. mp_timelimit is non-zero). This feature can be en/disabled with the gal_endofmapvote cvar to make sure that it's set to 1.
Make sure that you're game is up-to-date from Valve using Steam and ensure that you're using the official version of HLDS from Valve also.
Thank you very much for the quick help! the information received from the vote was very good. that works now!
but do you have an idea why he shows me this so strange during the map vote (r1 wcs_italy)?
see picture: photo