How to install Nextcloud on Debian 11.3

Nextcloud is free software distributed beneath an open-source license and can be used to set up a private cloud just like Google Drive, iCloud, Dropbox, and OneDrive. When using a client, the server is automatically synchronized with a local directory. Hence, the exact data stored on NextCloud can be accessed from multiple devices using a client app or via the web interface.
For more explanation on this video: https://www.linuxhelp.com/how-to-install-nextcloud-on-debian-11-3