Kinderzuschlag decision from the Familienkasse
A Bescheid is a letter in which an office decides something about your case.
What you can do
With a Widerspruch, you tell the office: I do not agree with this Bescheid.
The Widerspruch must be in writing. Sign it. A simple e-mail is usually not enough. You can also have it written down at the office.
Keep proof that your Widerspruch arrived. For example, a copy with the office's receipt stamp or a fax transmission report.
If you do nothing, the Bescheid usually becomes final when the deadline ends.