Hi @Micheck, just checked your github the code is fine. (I'm not a c# expert anyway).
For little comment you should consider give a real name to your form, that will help you to give them concrete responsibilities etc.. (but this really matter when code start to be big).
Another thing that you could consider is to put your project here : https://rathena.org/board/files/category/130-server-managerseditors/
I don't manage the forum so idk if it's correct in there but I believe it is.
Finally I don't know if you tough about this yet, but generally you want to have have a backup done regularly, like each day/week etc. Cause this is safer to just think of doing it time to time. To do this it would be interesting to have the program as a service. I know you could wrap it with https://nssm.cc/ or others, (you can also do a scheduled task). But I wonder if .net doesn't have something builtin for this. If you do this consider file rolling.
That what I had in my script, dunno if you checked it, anyway it's just a tough.
Good luck and keep the good work.