Klartext
Photograph an official letter and find out what it actually says.
Tax office, insurance, landlord, bank, immigration office. Klartext reads the letter and tells you, in plain words in your own language, what it says, when it is due, what it costs, what to do next, and what happens if you ignore it.
Every letter with a date gets a reminder before the deadline. Letters are stored on your device and nowhere else.