Do I lose all the notes on my device if I turn off ICloud notes?

No. If you go to Settings → Apple ID → iCloud, and disable Notes in the list, your iCloud Notes will be deleted locally from your iPhone, but NOT iCloud. When you enable Notes again, your Notes will be synced back to your iCloud.

You can see my Notes disappear from iCloud when I disable, and see it come back when I re-enable Notes:

Arh okay. If you want your Notes to be ONLY local on your iPhone in the future, go to:

Settings → Notes → Default Account → select On My iPhone.

In the future, all your Notes will remain local on your iPhone. You can move the notes you already have in iCloud to your iPhone's memory.

1. Open the Notes app

2. Tap Folders in the upper left corner

3. Select the folder with your Notes in the iCloud Category

4. Long press on each Note in the overview and select "Move"

5. Choose to move to any folder in the On My iPhone category.

That’s really helpful, thanks very

much😊