how to crop out unnecessary parts of a screenshot
Select everything you want to keep. Invert the selection. Delete everything that was selected. Then, use the background eraser to remove any remaining background fragments (so that squares appear, indicating emptiness), and then delete everything that was selected again.
Next, go to Image, option Trim, and crop the transparent pixels.
Finally, save the resulting image with the .jpeg extension.
Added after 32 seconds
Hehe, everyone has their own method.

Барон "Vampires"
Отдай свои прошлые сны,
В сомненьях себя обрети,
В бешеном танце душа кружится!
Не думай, что будет потом,
Здесь и сейчас мы живем,
Стань хоть на миг сам собой, слышишь!