アプリケーションを更新しようとしたときにデフォルトのオペレーティングシステムエラーが発生しました。

デフォルトのOS Hera 5.1（ターミナルまたはAppCenter経由）でアプリケーションを更新することはできません。

AppCenterにアクセスしてアプリ/システムを更新しようとすると、次のエラーが表示されます。

E: The repository 'http://ppa.launchpad.net/mpstark/elementary-tweaks-daily/ubuntu bionic Release' does not have a Release file.
W: Updating from such a repository can't be done securely, and is therefore disabled by default.
W: See apt-secure(8) manpage for repository creation and user configuration details.
W: GPG error: https://download.01.org/gfx/ubuntu/14.04/main saucy InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY FFACA3F86663559C
E: The repository 'https://download.01.org/gfx/ubuntu/14.04/main saucy InRelease' is not signed.
W: Updating from such a repository can't be done securely, and is therefore disabled by default.
W: See apt-secure(8) manpage for repository creation and user configuration details.
E: https://download.01.org/gfx/ubuntu/14.04/main saucy InRelease is not (yet) available (The following signatures couldn't be verified because the public key is not available: NO_PUBKEY FFACA3F86663559C)
E: The repository 'http://ppa.launchpad.net/pinta-maintainers/pinta-stable/ubuntu bionic Release' does not have a Release file.
W: Updating from such a repository can't be done securely, and is therefore disabled by default.
W: See apt-secure(8) manpage for repository creation and user configuration details

sudo apt-get upgrade以前に一般的に使用していたアプリを更新できましたが、今は更新するとこのエラーが発生し、実際には更新されません。

W: GPG error: https://download.01.org/gfx/ubuntu/14.04/main saucy InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY FFACA3F86663559C
E: The repository 'https://download.01.org/gfx/ubuntu/14.04/main saucy InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'http://ppa.launchpad.net/mpstark/elementary-tweaks-daily/ubuntu bionic Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'http://ppa.launchpad.net/pinta-maintainers/pinta-stable/ubuntu bionic Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

このエラーをどのように解決できますか？