Sudo apt-get update *not working, nothing really working well *REnewb

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W: GPG error: https://dl.winehq.org/wine-builds/ubuntu disco InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 76F1A20FF987672F
E: The repository 'https://dl.winehq.org/wine-builds/ubuntu disco InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.