Piracy: ꜱᴀɪʟ ᴛʜᴇ ʜɪɢʜ ꜱᴇᴀꜱ

Is returning it to a lower court overturning a ruling?

This sounds more like as described - "redo it". Overturning would be this court literally "over turning" and saying adblock is piracy.

No. This is how the legal system works. When you appeal to a higher court, they can make a call themselves when massive mistakes were made at the lower level or they can say the lower court overlooked something and then make them redo their work. It's a convenient choice for the higher judges not to have to do more work themselves. But it's part of the process.

To have a proper justice system.

As the main comment explained: this is not saying "you got the wrong result", this is saying " the way you reached that result is not the proper way for our justice system".

So they are just saying that the lower court didn't do it's due diligence and needs to look again at the case, this time considering the parts they missed the first time.

It is not uncommon in Germany that cases like this end in the same result

To try and explain it in an easier to understand way:

Person X murders Person Y

Court A says "Guilty, because you suck"

Court Higher B says: "Suckiness is not a proper judicial term, do the whole thing again"

Court A says "guilty, because here is the witness testimony, your finger prints on the murder weapon and the video footage of you killing person Y".

Same result as before, but this time in a proper manner fitting a proper judicial system.