I just bought Lightroom CC classic, desktop version. Xhen I want to open my existing lightroom 5 catalog, I get the question to upgrade my catalog, since I'm not sure I will want to use the new version I don't likt to upgrade my only existing catalog since I can not connect to it anymore with my old LR5. How can I backup my catalog, is it enough just to copy the files ?
That makes sense, but first you should know that the upgrade process will begin by copying your old catalogue and will upgrade the copy. So you could just go straight ahead.
But if you want an extra backup, open Lr5 and your catalogue, then go to Catalog Settings. This allows you to go to its location in Explorer / Finder, so then close Lr5, make a backup copy for yourself, and then you can go ahead with the upgrade.
It's the lrcat file that is most important to backup, and it's also important that you do know this file is your catalogue. It's amazing how many people don't know which file contains their Lightroom work, unlike how they know which Word document contains their will or which Excel file contains costings for rebuilding the garage etc. You should be backing up the lrcat file daily anyway.