When loosing one of my devices, I recover from other devices. Is that correct? Thx
If you only have always-online devices, remote message deletion and disappearing messages could both cause loss of information compared to if you had stored a monthly offline database backup at a safe place.
But otherwise, yes, data is synced between your online devices (minus the occasional network errors and bugs).
thx
Feel free to mark the topic as solved if your curiosity has been satisfied. 
your answer is a bit misleading what I got is that you are claiming that having manual backups is better, which is quite the contrary
having multiple devices is the best way of having backups, manual backups will delete disappearing messages all the same once you restore them, etc. and disappearing messages are meant to DISAPPEAR not to be kept forever so if someone is storing my disappearing messages permanently in some backups that is actually an anti-feature
to answer @stbaeumer yes you are doing it right, having extra online devices works as incremental automatic backups and you don’t need to do manual backups which are less secure and cumbersome and might actually cause lost of messages because if you lose the account you will only have the latest backup which will have missing messages received after it was created
Periodically saving offline backup files does not contradict with also running multiple online devices at the same time.
You can access content in ways other than by restoring a backup to a Delta Chat client.
I will still retain my authorship and copyright to all messages typed in by myself even if the given group has disappearing messages enabled. Hence, I have all rights to back up and even publish my messages as I see fit. Almost all groups I participate in has such a setting in place, so I would estimate that 99% of my messages have already been deleted by now. See here for a simple “oneliner” example you can run from cron to achieve this (I also index it and produce nice HTML from it)