Hello dear @Lydia,
thank you for sharing your question with the Wefugees Community.
Basically the Kindergeld is considered as income of the child and because the underage child lives with you, the Kindergeld is deducted from the total amount of money you/your family get from Jobcenter.
If your child is no longer underage and does not live with you and you send his Kindergeld each month to him via his/her bank account to him/her or you give him/her this money in bar and you have proof for that, you can regularly send this proof to the Jobcenter and the Kindergeld will no longer be deduced from your Jobcenter support.
I hope, I could have answered your question. I am a MBEON consultant. If you wish to contact me directly, you can have a **** at my profile and follow the instructions there.
Best wishes
Fardeen Noori