HI Markus, you can loop videos just like audioclips. So you need to turn on warping and the select loop (the button left to it in Live 11). If you play this in session with eSession view it will now loop the video. In arrangement view (with eArrangment) you will need to drag the cliplength longer to actually get it looping.
See also the manual: Clip View — Ableton Reference Manual Version 11 | Ableton
Good luck,
Timo