I took a video with my mobile phone, and when it was played, the picture was horizontal but not positive. How can I change the front and back of video pictures?

This has something to do with whether you hold your mobile phone horizontally or vertically when you take pictures with it. I suggest you try to record vertically and horizontally separately. How to modify the front and back of the picture? I usually watch it with thunder. If the picture is not positive, click Settings-right click the picture to rotate 90 degrees. After a few turns, the picture can be turned positive. Sorry, because I haven't done it for a long time. I don't remember exactly. Something like this. I'll go back and try the specific steps at night, and I'll add them then.