How to reduce the size of any movie downto ±800MB in VLC on Mac

[Sono97531]

To resume: I just want to reduce each film down-to around 800 MB, whatever its original size (mostly from 1GB up to 7GB).
For a couple of years I have tried to REDUCE the size of movies (avi, mkv, mp4, whatever)… without success. So every year I try again, especially as movies get bigger and bigger (without any added value but needing more and more enormous amounts of disk space).

The help found on the internet is useless. It indicated tabs, buttons or links… which simply does NOT exist on my Mac (VLC version 3.0.18).
I know 3.0.21 is the latest, but when I choose ”Check for updates”: NOTHING HAPPENS! No indication, no new window appears, no warning, no message, NOTHING!!!
OK, back to my problem.Movies tend to be more and more big in size, where every human interested in psychology knows a SMALL precision (like before) is 100% enough to enjoy a movie and every ecological person knows that 80% of internet pollution is caused by… insane volumes of pictures (photos) movies (films) and alike!
I tried to connect to the "The VideoLAN Forums" but… it doesn't recognise my PW anymore, and when I try the option "I forgot my PW" it it says it will send me an email but… this email never arrives; I even created a second email for a totally new user, IDEM: no answer at all.

Don't misunderstand me: EVERYTHING ELSE on the internet WORKS. It is just the help about VLC which is useless (see below) and the communication with the VLC forum.
Internet Help about VLC on Mac indicate I've to choose "Tools"… which doesn't exist, nor as a menu, nor as an option in any menu.

The option closed to reduce the size are:
• “Video>Crop”, as expected, only changes the window size.
• “File>Convert/Stream” is the same as “Window>File & Convert” and as the Save button keeps being GRAY nothing can be saved…

Thanks for all help you can give me.
PS: when I mark users (in another window, not to loose my quest), I don't see the list of user, so I can't copy them. How to do it?
How to find macOS members using VLC, and easily copy those?