(Solved) Signature-Error when updating OpenSuse Tw

Since this evening I have some problems with my OpenSuse Tumbleweed installation. I'm kind of a noob and everything I tried didn't work out.

When I try to update my system with "zypper dup" I get an error that the signature-check failed and if I still want to proceed:

>Signaturecheck for file "repomd.xml" from repository "repo-oss" failed<

I downloaded the GPG-Key from the OpenSuse Website, deleted and reimported the new key. This didnt help.

When I deleted the key and didnt import a new one the system imported it itself when running zypper dup. Fingerprint was the same as before.

I had the same problem with an other repository but reimporting the key worked for now.

Can someone help me on this? Can this be some kind if temporary problem?

--- Update ---

I tried everthing for 2 hours.

Now the error isn't there anymore and I can update without problems