Hello Peter,
You need to prepare the Keepass File before you can import it and delete the Attachments inside the Keepass File.
I have done the KeePass Database Maintenance, not sure if that helped too.
If you have ä, ü, ö, ß, or similar characters you should change them after the import to Passwordstate, by exporting afterward from Passwordstate again and doing some find and replace, it is easier.
greetings from Tyrol
Marcel