If you are unable to mount a Mac APFS drive and the built in tools don't help, you can ask the assistance of Stellar data recovery technician for mac.
With this tool you can scan the drive and you ahve high chance of recovering data and saving from the volume.
If you see the folder empty where you stored your very important data, run the "Deep scan" which might take a while, but most probably will show you your files
If it doesn't help you might want ot find a company which can restore data from corrupted SSD
