I created a dump the way you said. Restoring with the webpage still gives me an error. If I refresh the page afterwards I see the new database. I can choose it to login with, but the data hasn't been restored. (users don't exist, password of admin user is the default one,...). Restoring by commandline (pg_restore you provided) restores the db, but I cannot see it in the database manager. Any idea what I am doing wrong?

reboot your postgresql server that error came when the database is in use from another pid

I found it, The owner of the database I created with the commandline was wrong. I altered the database to set the correct user and now it works. Thank you.