per the manpages for gpg,

-d

Decrypt the file given on the command line (or STDIN if no file is specified) and write it to STDOUT (or the file specified with --output). If the decrypted file is signed, the signature is also verified. This command differs from the default operation, as it never writes to the filename which is included in the file and it rejects files which don't begin with an encrypted message.

so -d was working fine, but it was decrypting the file to the STDOUT, which is why you saw a bunch of junk output. that is the encoded data for your .tar file, so its no surprise its gibberish.

if you want it to decrypt to a file instead of your shell output stream, use --output <filename> or redirect output to a file.

I believe (I can't read German) that when you ran the command on the file, it assume it ran the equivalent of

gpg -d no1.tar.gpg --output no1.tar

per the manpages for gpg,

-d

Decrypt the file given on the command line (or STDIN if no file is specified) and write it to STDOUT (or the file specified with --output). If the decrypted file is signed, the signature is also verified. This command differs from the default operation, as it never writes to the filename which is included in the file and it rejects files which don't begin with an encrypted message.

so -d was working fine, but it was decrypting the file to the STDOUT, which is why you saw a bunch of junk output. that is the encoded data for your .tar file, so its no surprise its gibberish.

if you want it to decrypt to a file instead of your shell output stream, use --output <filename> or redirect output to a file.

I believe (I can't read German) that when you ran the command on the file, I assume it ran the equivalent of

gpg -d no1.tar.gpg --output no1.tar