How do i get off the back wheel bar attached to wheels ? I need to send it back.
Well, it is not easy, so rather ask your partner or dad (or anybody technically skilled, at least a bit) to help you. There should be two small, tiny metal pops needing to be pushed in to release the part, but again, as I say, it is not easy. Best is to consult the Hauck Sport's manual, and/or watch an unboxing video and try to notice what clicks in where (and detach it by doing the opposite process.
I am attaching a screenshot of where you should be searching for the metal poppers to push in and to pull the bar out while they're pushed in:
P.S. If you still cannot do it, try to call the customer service, they should help and navigate you as well.