I know only one cause of this problem and only one solution that worked for me. This error appears if you have non-English characters in your system path to “Documents” folder. Why is this really important? Because this game keeps your save files in that folder. So “Runtime error” could appear once you saved your progress in the game.

But you can check path to the folder by yourself. This could be done in many ways but here I show you my steps. Open “File Explorer” window and right click on “Documents” folder and after that choose “Properties”.
Screenshot here:


In opened window under “Location” tab you will be able to see your real path to the “Documents” folder. Make sure there are no non-English characters in every folder name in this path.
Example:

So what can you do if “YOURNAME” contains non-english characters? Everything depends on version of your operating system and type of your Windows profile (local/online). I think the best thing that you can do is to check on the Internet how you could change existing user name on your system or maybe how you could create another user on the PC. It will be better solution instead of putting here a lot of information about different cases and solutions that I even can not try by myself.

But if you need to change name of your “Documents” folder I can help you here. Before you start doing anything please make sure you fully understand about possible risks if something goes wrong.
You need just click on the “Move…” button and choose another empty folder without any non-english characters in their name. Press “OK”. You will be asked about transfer of all your files from old folder to the new one. Just answer “Yes” and wait until it is done. Example here:

This solution worked for me and I changed name of the folder from one language to another. My “User name” on the PC already was in English so I only needed to change name of “Documents” folder. After that game works fine.

Hope you find something useful in this small guide or create your own ways to solve this problem. Thanks to everyone who posted information about this error on the forum.