Thank you so much for trying to help me! I downloaded the file you sent me, unzipped it and started it, but it just tells me "RPG Maker 2003 not found" in an error message and shuts down.
However, I tried some other things: After confirming that my other RPG maker games were not made with RPG Maker 2003 but other versions, I downloaded a free RPG Maker 2003 game and that game indeed suffers from the same/similiar problems as Ara Fell (besides the Alt key, in that game the z key works as if it's the menu key, but that's all - no arrow keys or anything). Meaning it's a problem on my end and I started checking what it could be.
What I found: When I restart my computer with my mouse and my Internet device (some mobile internet webstick) unplugged and then start the game, it works! :D But as soon as I plug any of the two devices back in, it stops working immediately. Even if I have it open. Having Ara Fell open and plugging the USB-device(s) in also causes my laptop to go into CPU-eating frenzy for a few seconds while normally it doesn't care at all when I plug my mouse or webstick in. When I unplug the USB-device(s) again, the game still remains unresponsive. Meaning that I can play the game - which I am extremely happy about - but I cannot use my internet or my mouse or I will have to reboot to play again. Which is very inconvenient since I'm 100% a person who likes walkthroughs to get every single thing in video games and I also am bad with a touchpad, so both internet and a mouse would be helpful.
Right now I'm happy that the game works and I hope it will continue to do so and that I won't run into the "sticky key" issue on top of the hassle I already have. Thank you very much that you guys look into fixing these issues for good! I would love to not have to reboot my computer every time I want to play. ;) But right now I can work with this and I have a lot of fun exploring Aloria at the moment. :D