Hi @yamimiriam On this issue please ensure you have the SD card as Portable before removing or reformat it as such, but see the link appended. To confirm it is portable check Settings > Storage and ensure you see an eject symbol to the right of the the SD card. Do not remove it if you do not then see the link appended on how to remove after transferring apps etc.
You may have to do a Factory Reset, but as @OldRoutard said please contact support[at]fairphone[dot]com soon.
You may like to try dissembling and reassembling also.
Good luck