Is that the right screenshot? Showing in msg.payload an array of length 1 containing an object which contains a statement_id and an array called series?
That is very odd data coming from influx. I don't even know how I would get data like that into the db.
Edit A big problem with your Change node (if I understand the German?) is that the first line overwrites msg.payload[0].series[0] to "A", then in the next line you try to access the payload value, but you have just destroyed it.
You will need to first move msg.payload to msg.save (for example) and then move it back from there into the payload.
