Hello. We solved it by upgrading for one month, paid the 7 € / month and cancelled directly. It's frustrating as i pay now for a bug - that's how it feels. By this i was able to recover the data from the history menu. That was really easily and quickly done.
But i will remove all my data now from Evernote. This is too unsafe for me - i don't want this to happen again. How can a function like "data history" be so hidden and price-tricky. I'm disappointed by this management practice. It's certainly not a virtuous practice.
Still, thank you very much for your kind and quick offer to help. That really was a big help! Greatly appreciated.