AOC Monitor 21,5" 22B1H as second display for MacBook Air (13-inch, 2017) does not fill up the second screen

I've just acquired an AOC Monitor 21,5" 22B1H as second display for my MacBook Air (13-inch, 2017) macOS Catalina Version 1.15.7. But here is the issue: sometimes the AOC screen is totally filled up and perfect and other times it is not - there are large black margins as a frame. Has anyone faced that?

I can't install the driver from AOC made for mac: drivers\bf29992c-faba-42e8-87b5-d7226b7fb8a3\22B1W.INF because it does not run on MacBook and the mechanical bottom from the AOC monitor with Image Configurations is not available on the monitor.

Besides that, here is what I found on AOC.COM <https://mm.aoc.com/faq.php>:

Do you have drivers for the Mac?

A. To use your monitor with Mac, you will need to install the Plug and Play driver that is offered by your Mac operating system. For information on how to install the Plug and Play driver on your Mac operating system, please contact Mac technical support.

But, my Mac does not have support from Apple anymore. For the love of all the goddesses can anyone help me?