Is there a site somewhere where I can save a video from my cell phone and then download / save the video from my laptop back to the site?
Google Drive, OneDrive, Dropbox etc. ^^
Send YouTube or just email yourself
I think 20 minutes are too long
We transfer or connect the good old usb cable to the laptop
There's so-called cloud storage for this.
There are various (free) providers, such as Google Drive, Dropbox, etc.