Sequence problem

I'm working on a simple sequence using mov files in premiere 2020. I downloaded these files from my iphone via "web.airmore". The original files are correct, audio and video. However, when I create the sequence with these videos, the audio does not synchronize correctly with the video, even if I have not made any changes to the original file. I also notice that the video seems to "jump" from one frame to another, and rendering doesn't work to fix the problem either.
If I have a long shot and want to select several moments of it to create a sequence, after a few minutes, all the selected pieces become the first selected one, my sequence turnes into a loop of the first selection made from the original clip.