[nick46]

Right calling all computer geeks, I need some help please.
Today we had a bit of a family day out and I recorded some slow motion videos of the kids doing some tricks on a trampoline using my Galaxy S9 - just normal slow motion not the super slow motion function. I've cropped the videos so that just the footage I want plays and saved on my phone. I now want to transfer the videos onto my laptop and my external hard drive like I do with all my pictures and videos. However, this is where the problems start. I can save the videos as I normally do but when I play them back I just get a black screen. I do however get the sound.
So, how do I get the slow motion videos to play on my laptop?

Can any answers be explained in simple, easy to understand English please as I dont really get on with computers that well and I certainly dont understand all the computer lingo!