Get error: the following signatures were invalid: EXPKEYSIG 4FE13824E3FFC656 on Linux

Now I’m wondering how can I install it the proper way on POP OS?
Also I found this: [HELP] An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://brave-browser-apt-release.s3.brave.com bionic InRelease: The following signatures were invalid

Someone said:
" You have to verify the new signing keys – please see this thread for more information:"

But I have no idea what is “signing keys” If you can help me with that, would be awesome

Many thanks in advance for the help!