Just format the disk / delete the partition (before or during the installation of Debian 11) if you use physical machine, or remove the vm and create a new one if you use virtual machine.
Debian installer offers the choice to overwrite the existing installation. If you read the Installation Manual, it is chapter "6.3.4. Partitioning and Mount Point Selection". https://d-i.debian.org/manual/en.amd64/ch06s03.html#di-partition Also: https://forum.howtoforge.com/thread...or-a-first-time-linux-user.83782/#post-399369
To uninstall and reinstall Debian 11, you'll need to follow these steps: Backup your important data: Before you proceed, it is always recommended to back up any important data you have on your system. This will ensure that you don't lose any important files during the uninstallation and reinstallation process. Boot from a Debian 11 installation media: Insert the Debian 11 installation media into your computer and boot from it. This can be either a DVD or a USB flash drive. Start the Debian 11 installer: Once you've booted from the installation media, you should see the Debian installer. Follow the prompts to start the installation process. Select the partition to uninstall Debian 11 from: When you get to the partitioning section of the installer, you will see a list of partitions on your system. Select the partition that currently has Debian 11 installed on it, and choose to delete it. Install Debian 11: Once you've deleted the partition, you can then create a new partition and install Debian 11 onto it. Follow the prompts to complete the installation process.
