When I joined, I had a lot of misconceptions also.

Nostr is mostly about anti-censorship. And even that, it’s not always true. 

Nostr does not guarantee privacy. 

Your notes are out in the open, the pictures you upload, etc…if you are not using a VPN, you are giving away your IP address to the relays owners…

The relays have policies that are not known. So no one knows what will happen to your data, how long it will be kept, etc…