Hi @christianbusson
Here's a [https://www.youtube.com/watch?v=DvPs93WLlpk|video] that may help.
At 58 seconds (0:58) into the video, the fan can be seen being loosened from its mounts.
Search online for [https://www.google.com/search?client=firefox-b-d&q=13PT01M1P02011|13PT01M1P02011] to find suppliers that suit you best. (supplier examples only). This is the Asus part number for the fan used in your AIO.