Nextcloud wreaked havoc on my computer!

I encountered a problem when attempting to open one of my programming project, but all files seem to be offline. I resorted to installing the newer version, 3.2.1, from 3.1.4. It must be my biggest mistake.
After the installation, tons of fake “delete files” operations are created, or so I believe, and then files are really deleted from the server AND the client! All went unnoticed, so I’ve lost 90% of all syncing files.
I hope there’s a way to restore…

the magic word is: backup! just restore your newest backup (hopefully from the day before everything started to happen)

and: we know that you’re in panic but nevertheless: we would need some more informastions about your system and environment

Client is Windows and Server is Linux. Sorry, but what environment?

well there’s a template coming up here if you decide to open a thread. fill in as much as possible from what asked.

i have made great experiences with app issue template from appstore.

Now that I’m controlling my mood…I must admit there’s fault on myself.
Days ago, as the 3.2.1 is released, I installed it and turned on Virtual Files. It worked fine at first, but due to an unknown operation, nc would stuck on startup. I discovered deleting the db files nc created would help, but I still rollbacked to 3.1. Strangely, the cloud icon persisted.
Today, as I said, I tried to open my project, but notified I’m not allowed to open any files for they are online. I made a fatal prediction that it would be solved in 3.2, and I upgraded.
As it is done, all syncing directories have a duplicate, and I manually remove one of each. It said such would not delete any files.
And now…

If I still need to fill out the thread…How can I obtain the template again?