Now I really have to use MS Office applications for my school. Libreoffice is good but not completely compatible

Indeed it is not. It all depends the tools you have to use and your level of expectations. But you still may want to some research to see if there is no simple fix available?

How do you guys manage to open MS files appropriately?

I don't try to 'manage'.

I mean, if it's work-related (aka with a deadline and clients waiting for me to deliver) and if I need full compatibility or a very specific set of Office tools and have no alternatives, I simply use a Windows PC with Office installed on it. I would only use it for that purpose, though, as I don't want Windows to get their dirty hands on my files, but I would use it.

BTW, there is no need to spend a fortune on that machine/Windows key. Office will run fine on older hardware that can be purchased for dirt cheap used and that Often comes with a Windows license. Maybe you PC has its won Windows license you can still use.

Also, since you're a student, your school should provide you with an Office sub or something like that, or they should not be allowed to require you to use it.

One other thing you may want to do is explain your teacher the issues you and maybe other students are facing by requiring you to use tools that are not relying on open standards. Maybe also suggest alternatives if you know some?