How to download videos from Twitter:
Open Twitter, and go to the tweet which contains twitter video.
Get the link/url of the tweet which have video.
Method 1: Click on the tweet, and copy the url from address bar of the browser.
Method 2: Copy click on the three dots(...), and click on "Copy link to Tweet"
Now right click on the tweet url and "Copy link address".
Paste the tweet link in the above input url box, and click on "Download" button.