Last month I decided to try a premium function and upgraded to a premium account (while I had oved 200 presets already on my beautiful free account). Well, as I upgraded I lost EVERYTHING. Presets, pictures, everything! I tried to contact support but was left unread. I'm so mad and I don't know what to do now.
I sorry for this bad experience. Do not uninstall the app -- your missing files are still in the application cache and deleting the app will also delete files you have not yet synced. Please backup your device, and then try the advice on this page to try and recover your original images:
If you are not able to recover files, do you have a recent back up of your device from a time when Lightroom still had your images? If so, restore that backup onto your device and then try the help steps again from the link above.
How can I know if that by doing so I don't really lose everything? Also how could I know what backup had the lightroom presets and how could I restore that one if so? The tutorial doesn't seem to explain a lot I could understand to be honest
After you have successfully backed up your device, you can later restore your device exactly to that same state with all the files and settings on your device as they existed before. It's important your backup your device now if you have not yet done that. This way you can be sure nothing will be lost.
The other page I shared talk about how to use iTunes to browse the files on your device that are still inside the Lighroom app. If you have Mac OS 10.15 or newer, the functionality has moved from iTunse to Mac OS Finder. Apple has a newer Support page that describes how to use Finder: https://support.apple.com/en-us/HT210598 Is this Apple page clearer?
One thing to note: this advice can only help recover images in their original state. Unfortunately, it cannot help recover presets.
Taking a closer look at your account, I see you had a subscription that ended on January 16, 2021. I will send you a direct message with some additional suggestions.