iPhone Notes disappeared after iCloud sync enabled

Hey All, I have problem regarding my Notes. Hundreds of them disappeared from my iPhone stored folder, when I turned on icloud sync. It happened in front of my eyes, the merge vanished my iphone stored notes and replaced them with some old ones, that has been backed up from an other device earlier. I saw, that other people had same problems, yet, I found no solution. I tried to add my iphone stored folder in the notes app as default, as well as I tried to sync with my gmail account. Turning on and off the phone, as well as the sync of icloud. Thank you so much for your advice.