If i update my C5 version may loose all the work that i´ve done in my site?
PermalinkTake both an 'all files' and a database backup first. That way you can always get back if it goes wrong. If you don't have both backups, it could be a one way street. 99.9% of the time it will be simple and no glitches. The other 0.1% and you will be wishing you had those backups.
Swap your theme to default during the upgrade, then swap it back again once you are sure all is ok. That will make sure there are no theme issues during the actual upgrade.
Obviously some blocks are not always compatible but most blocks are now. I have done numerous updates to my clients' website and all has been ok. There are sometimes a couple of tweeks to change.
Good luck