Based on the instructions in the Support udpate webpage I just need to upload all the files and folders?, this means the FTP program is going to be asking if I want replace all of them, is that correct?, But my brain thinks based on the the windows operating system, if I replace files and folders all the data is going to be firstly deleted and then replaced by the new ones, am I wrong?, if I am right this means all of our data is gonna be “memories” (I hope to be wrong !!).

I use Filezilla, and on a Mac it does not delete-folder-and-replace like the Windows OS does it, rather, it replaces individual files, leaving old files in place. I am not sure how it will work on Windows, but I guess you could do a little test to find out. Create a directory with three files and upload it. Then, remove one local file, and add a new one with a different name. Upload it, and you should end up with 4 files on the server.

Thanks Ross, for the test, that is the expected behavior, the new file is just gonna be added to the directory and the first 3 are going to stay in the server without changes.
I´m gonna try to be more specific, I have 3 files, file1.txt, file2.txt and file3.txt in the server. In my computer I´m modifying those 3 files, then I save changes, if I upload those 3 files using filezilla to the same directory in the server its obvious the files in the server will be “replaced”, my doubt is if those changes will affect the system, that is my main concern !!

On upload, you will have a choice to keep current files or replace them, depending on age. So, if your changes are newer, you could, in theory, save them. However, those files would lose changes we have made, which might cause serious issues.

General wisdom is to not make any code changes in the core that are not contributed back, otherwise updating becomes a nightmare. You could, if you had to make changes that could not be contributed back, keep a list of your changes, and make them again after upgrading.

Hope this helps!