"Just to save to mp3 I'm having this problem and I don't know how to solve it. I already uninstalled everything, restarted it and it didn't work sound forge 17"

Rsetting Sound Forge has been known to resolve MP3 encode issues 'File> "Reset all preferences and clear cached data"

You might try using the 'legacy' MP3 encoder. To re-enable it, search "MP3" in the (hidden) internal menu. (to access the menu, hold down the Shift key and click "Options> Preferences" which will include the "Internal" tab.

btw, welcome to the Magix Sound Forge users community @klairus-siqueira.