Video MP4 in Powerpoint for Mac doesn't work after saving file

[LVA]

Hi,

I'm making a powerpoint with a lot of videos in it. If I select a video and put it in the powerpoint, it plays without any trouble. But when I save my powerpoint, exit it, and open it again, all of the videos are saved as pictures. So I can't play any videos.
The way I select my video is:
Insert - Video - Video from file

What am I doing wrong?

Thanks in advance!