linux – Can’t run sudo apt get update on Update PHP on Google compute engine

I want to update my PHP version on my VM and for that, I have to run sudo apt-get update on my VM in compute engine (google cloud platform) But I keep getting an error saying public key not available

Here is my environment:

Linux wordpress-1-vm 4.9.0-5-amd64 #1 SMP Debian 4.9.65-3+deb9u2 (2018-01-04) x86_64 GNU/Linux

Here are the errors I get:

Ign:1 hirsute InRelease Err:2 hirsute Release 404 Not Found Reading package lists... Done E: The repository ' hirsute 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.

Can someone help ? please