Hi,
gpg is informing you that the public key you have imported has been signed by 56 others. To verify those signatures, you’d need to import 56 more public keys, belonging to each of those individuals. Some may be expired and some may not be. Unless you already trust any of those other 56 individuals it is quite irrelevant to you.
You can strip out those signatures, leaving only the self-signature of the public key you imported by:
gpg --edit-key <key-ID>
minimize
save
now if you do
gpg --check-sigs <key-ID>
you will see only the self-signatures.