Installing clang on debian 11

Question

I am on Debian version: 11.6 and trying to install the clang package by running:

sudo apt-get install clan

However I am getting:

Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
E: Unable to locate package clang

I have tried with specific versions: -6 or -7. I have ran the following commands as advised in multiple posts:

• sudo apt-get clean: does not change anything
• sudo apt-get upgrade: run successfully but still same error
• sudo apt-get update: getting some weird error:

Get:1 http://repo.mysql.com/apt/debian bullseye InRelease [17.9 kB]
Hit:2 http://repository.spotify.com stable InRelease                                                                 
Hit:3 https://download.docker.com/linux/debian bullseye InRelease                                                    
Hit:4 https://linux.teamviewer.com/deb stable InRelease                                                              
Err:1 http://repo.mysql.com/apt/debian bullseye InRelease                                                       
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY B7B3B788A8D3785C
Hit:6 https://dl.yarnpkg.com/debian stable InRelease                                      
Hit:5 https://cli-assets.heroku.com/apt ./ InRelease                
Hit:7 https://packages.microsoft.com/repos/code stable InRelease
Hit:8 https://packages.stripe.dev/stripe-cli-debian-local stable InRelease
Reading package lists... Done
W: GPG error: http://repo.mysql.com/apt/debian bullseye InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY B7B3B788A8D3785C
E: The repository 'http://repo.mysql.com/apt/debian bullseye 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.

Not sure what the issue with mysql or how to solve it nor whether this is really what is preventing me from installing clang?