There are three ways:
1. Start playing video in full screen and tap download icon in the top right corner:
2. On the web page tap and hold video element then select 'Download video' from the menu.
3. If you have a direct link, go to 'Downloads' and tap "+" icon on the bottom right corner.
URL will be pasted automatically from the clipboard if there is any. Tap 'Download' to start download:
Please note: If you can't download from specific website or your downloads come up broken, please report URL link to firstname.lastname@example.org