I like to use Anki with some shared card decks: https://ankiweb.net/shared/decks?search=german
The learning pattern that Anki has configured by default suites me quite well and the app and the card deck is highly customizable.
Mind you, this is mostly only for learning vocabulary, not for learning grammer.
I don’t know if this will keep the labels, but you can try to sync your contacts via DAVx5 to your nextcloud instance. Use https://f-droid.org/packages/at.bitfire.davdroid on both phones, this app syncs calendars, contacts and notes. In the setup it should be enough to login via URL and credentials. If you run into problems with this setup, let me know, I can try to assist you :)
Once you got that set up, it is a neat way to keep your contacts backed up and synced with other devices like a PC. If you want to dive further into the syncing without relying on Nextcloud, I recommend Baikal.
Good luck!
I don’t know where you got “a couple of years old” from. Do you mean, that the Fairphone 4 in general is a couple of years old?
Because, on the website it says the refurbished devices are: “After less than a month of Fairphoning, the phone is returned” So the Fairphone was only in use for max 4 weeks. I would still count that as mostly first hand :)
What do Jesus and the floppy disk have in common?
They both had to die to become the symbol of saving.