I succeed enter the partitions but against my hope the file was already replaced and unrecoverable.
Anyway i managed to extract meta.db and meta.db-wal from a backup file (made in the past with backup menu) and I copied them over to my system.

After restart all the contacts are there but I can't add any new ones. When I try - the moment I press save the contacts app stales until reboot.

Any suggestions?

( I've checked ownership and access rights of meta.db extracted from backup and they seem the same as the original file. )

(Also I've backed up contacts with Nokia Suite and then reverted to original meta.db [with which I can add new contacts] but then Nokia Suite won't copy them back to n9 giving some error code)