See this article (which also contains relevant links to others): How do I set up Sync on my computer?

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Thanks.

It's not a solution for me, I don't won't to sync main computer with another device by connecting this other device. I'd like to have my oryginal data which I synced for the very first time. I was hoping to get all the data from the server which are connected to my account via email or something.

If you've replaced the data on the server by inadvertently using an old file to sync with, then the orginal data has been wiped.

It's the same principle as downloading a file for which there is already one on your PC with the same name. The new one overwrites the old one. If it didn't then you'd forever be faced with only ever having the original data every time you synced.