I made several videos on my Huawei P20 lite and downloaded them to my PC Win10. All videos up to 100mb can be played without any problems. The bigger ones are not. No matter which player (Media, VLC, Quick Time) someone has an idea.
Is the GraKa from the PC, you can probably change nothing. Maybe try with Linux.
Have now tried another laptop and the TV but the videos do not work unfortunately.