can you guys help me is it all right can i use this app now there is something wrong still i can"t understand
gpg: Good signature from "F-Droid <email@example.com>" [unknown]
gpg: WARNING: This key is not certified with a trusted signature!
gpg: There is no indication that the signature belongs to the owner.
The warning is shown as nobody from your own keyring has signed F-Droid's key. The wiki describes how you can verify and then confirm the key yourself, so the warning goes away.
A newer server operated by the Mastodon gGmbH non-profit