export with bad sound

hello, i tried a few times to export my project,
tried mp3, flac, wave - and with every one of them the sound that turns out is not as what in my project.
my cubase teacher and many people saw the Export Window but they all say that it is okay.
The main thing I notice that changes in sound is the bass instead of being kicking and strong, it is with a kind of delay and low.
Beyond that, some of the instruments simply disappear from the song.
please help

Hi and welcome,

Where do you hear the song after the export? Do you use the same Audio Device, same speakers?

What happens, if you import the project back to Cubase and listen to it from Cubase?

Do you use any plug-ins on the Monitor Control Room bus?