Q: How to delete folder "videos from my computer"

Howdy Bluestarcastic,

Thanks for using the Apple Support Communities.

I see from your post that you're seeing some videos on your iPhone that indicate they're from your computer.  This means that the videos have been synced to your iPhone by using iTunes.  In order to remove these videos, you will have to remove them from your syncing options as described below.

Delete synced photos

1. In iTunes, locate and click on your device.
2. Click Photos.
3. Choose "Selected albums" and deselect the albums or collections you want to delete.
   To delete all synced photos, deselect "Sync Photos from" and, when asked, click "Remove photos."
4. Click Apply.

Learn how to delete photos and video synced from iTunes when you can't access the originals.

Sync photos from your computer to your iOS device using iTunes

Cheers.