Thanks for the replies. I couldn’t do it but I already waste the saturday trying to do this so it’s just time to move on. I can say shotcut was the closest program to help me with it. With other programs I couldn’t even get to the “trying to crop the part of the video you actually want” stage.
I clearly went with the wrong mindset, probably spoiled for doing it mindless with pictures in paintnet for years. Open pic, select, crop to selection, save and that’s it. I assumed, clearly wrong, that video should be the same. Open vid, select the actual part of the video you want (in my case, I just wanted the vertical square where a person is doing sign language in some news channels), crop that part, save it and move on. No idea why would I want only a part of the video visible and the rest… as black painted background? But I assume is some sort of effect. At the same time no idea why would I want to zoom-in to a part of the video unless, of course, I explicitely select a zoom related tool. Or why would I wanted to maintain the same resolution while selecting and cropping a smaller part inside a video? If the video is, let’s say, 1920x1080, and the part I selected is something like 260x450 (my ignorance makes me wonder if a resolution like that is possible in a video, I assume yes), I expected the new video to be at the resolution of the cropped part (260x450) and not catastrophically pixel-zoomed adapted at 1920x1080 resolution.
This is just beyond confusing for me and, clearly, I’m not gonna get it since it looks plain unnatural for me. In any case, thanks for the help regardless. I didn’t want to just delete my account without at least thanking the help to try overcome my clumsy attempts at this.