Good Afternoon,
I'm Cletus(a Web Developer using Kubuntu Linux Destro), and I want to switch to Debian (that was my first choice of Destro, just that I wasn't able to install and configure it)
So I want to know wether it's possible to switch to Debian without looking my files ?
N/B: I'm running Kubuntu and Windows currently (I still want to keep my Windows)
The *proper* way to do it is to back up all your important files, and then repartition your drive as needed (or add more drive space in some other manner), and install Debian.
But ... a second option is to use your existing Kubuntu partition[s] and install Debian onto those partitions, destroying the Kubuntu that is already there. If your Kubuntu has a separate /home partition (or wherever you store your personal files), you can just tell the Debian installer to use that partition for your Debian /home directory, without erasing/formatting it first. Be aware that in either of these three options I present, Kubuntu config files in your home directory may not be 100% compatible with their Debian counterparts, such that Program X on Kubuntu may not work [properly] on Debian using Kubuntu's version of the user's Program X config files.
A final and third option, which is almost certainly going to lead to severe broken-ness, but with enough effort and perseverance can eventually be repaired, is to change your Kubuntu's /etc/apt/archives/sources.list (and related dirs/files, as needed) to point to the Debian archives instead of the Kubuntu's archives, and then do a dist-upgrade. This is the option I'd try, just to see if I could make it work, with the understanding that I would likely give up after two days of fighting it and just start over with option 2 above.
In any case, you should make sure you have a working backup of your important stuff, and you should expect that something will go wrong and make your machine unbootable, either into Debian or Kubuntu, or even into Windows, and be prepared to fix the issue (such as running whatever Windows's boot-repair option is available on whatever version of Windows you have).
If you enjoy tinkering, you can have a lot of fun and learn a lot. If you just want things "to work", you may just want to stick with what you have.
"Success to you" in any case!