You have to be insured while living in Germany. There are a few scenarios in which you might want to cancel your public health insurance membership: switching providers, leaving Germany permanently, and leaving on holiday.
I want to switch my provider
This template is used if you want to switch from one public provider to another, or if you want to switch to private health insurance. The time to cancel in this case is the end of the current month + two months. For example, if you cancel on November 2: then you're covered until the end of the month (November 30) plus an additional two months (January 31).
Your new health insurance should then be applied for to begin on February 1. Just download the form, and edit all the highlighted areas with your personal information. Then either send it by email or by letter to your health insurance provider. Be sure to send a copy to Feather at email@example.com.
I'm leaving Germany permanently
In this case, it is usually enough to inform your provider. If you signed up via Feather, then just letting us know that you're leaving is usually enough (firstname.lastname@example.org or in your account). If you didn't sign up via Feather you'll have to go to the provider directly. Sometimes, additional proof like an Abmeldung (de-registration from your city) or flight tickets might be required.
I'm leaving for a month of holiday
In this case, you can't pause or cancel public health insurance. Which is a good thing. If something terrible were to happen, you'd be covered when you get back.