I think this is the problem: SDL2 depends on other libraries that my teacher hasn’t or he has in different versions.
Yes, the problem is that you have a newer version of GLIBC than your teacher.
You could extract the libs you give to your teacher from packages of older Linux distributions or from the Steam Runtime, that should be more compatible (though packages from older Linux distros will have older versions of SDL2 and SDL2_Mixer, which sucks if you need features/functions that have been added afterwards).
Or you build SDL2 and SDL2_Mixer yourself in a chroot or Virtual Machine running an older distro.
My teacher said me he won’t try again to build my project. The next time will be the official one :’(
But also your teacher sounds like an asshole (and kinda incompetent if he couldn’t tell you what’s wrong with the libs you bundled and how to fix it), so choosing a different project might be a good idea if it doesn’t have any disadvantages for you.