To backup your wallet. Go to your commercium folder, look for wallet.dat and backup to another storage. Do not share that file.
Secondly..until, the latest wallet release..you may extract the bootstrap and save onto your wallet folder. Normally located on your %appdata%\commercium folder.
This may improve the synchronization of wallet to nodes.
http://node.bitcoin.tt/bootstrap.zipHappy mining!
Thanks. So, there is no need for private key?
If something goes wrong I just replace wallet.dat with backuped one and everything will work?
Best regards