To get the SD card navigation to work, the car needs to have the "Pre-installation for SD-card navigation" option. I can't see where you are located, but in the USA that's a $200 option. The SD card alone won't work unless the car was ordered with the pre-installation. The other option is the Multimedia package, which would give you the full COMAND navigation (no SD card required). In both cases you still have CarPlay and Android Auto available. If the car has neither option, then your only choice is CarPlay or Android Auto. There are navigation apps with CarPlay support that have offline capabilities, so they work when you don't have a cell signal. The best is HERE Maps, which is the technology that MB uses for their built-in navigation systems. You can download entire states/countries to the phone for offline navigation. Google Maps also has offline support, but it's a pain to stitch together enough areas so you can navigate continuously while not having a cell signal.
https://apps.apple.com/app/id955837609
To check what options this car has you can enter the VIN here and see the detailed specs:
https://www.mbdecoder.com/. I don't know what the option code is for the "Pre-installation for SD-card navigation", though.