Hi! Sorry for the late reply.
I had to use a different PC since it was important for me to use the program for work, so I was on another computer.
Anyway, following the method everyone here kindly suggested, I created a new Windows account on the problematic computer and ran InDesign, and it worked without any issues! I also tried entering safe mode, Windows updates, etc., but they all failed in the end... so as a last resort I even tried PC recovery, but that failed too. (I had Windows updates set to automatic and wasn't paying attention to it, but through this I found out it had actually been failing every time for almost 2 years 🤣)
Then... I noticed an icon I don't even remember installing, and when I tried PC recovery through that, it actually worked! (It's a program called 'Maestro Recovery' — I wonder if that's used in other countries too?) Anyway, it seems like this program had been blocking the updates. So now, after going through recovery and updates, I'm using InDesign without any problems.
Anyway, since the situation was so frustrating, I ended up solving it with the primitive method of reinstalling Windows... but since Illustrator and Photoshop worked fine without any issues, I didn't think it was a Windows version problem... is there something you suspect could be the reason InDesign wasn't working, based on the method I used to fix it? Could it be that something among the apps on my account was conflicting with InDesign?
And thank you for taking your valuable time to help with my problem and for caring about it.
Have a great day!