Who knows if this is about batteries, or taxes, both have been brought up, so . . .
Your question was a little contradicting / confusing.
Why ask about taking it onboard unboxed, when you say you'd prefer it left in the original packaging ?
I think you are worried about batteries only ? If yes, rightfully so.
You'd have to check local rules on carrying LiPo batteries, though most airlines are the same or very similar.
Some special ones like Emirates seem to have their own rules now, so best to ask.
Here in Australia, you can take batteries up to 100Wh rating (the MP batteries are 43.6Wh, check Air specs but suspect well under the limits), cabin bag only.
There are NO limits on how many you can take though, I routinely travel with 4 MP batteries, and sometimes even the Spark too which I have 2 batteries for.
You will HAVE to take the unboxed (or individually boxed) batteries into cabin though, and this may require unboxing the main package to get to them.
The drone and accessories are no problems checked, though I take all my kit in cabin bag to avoid baggage handlers who can be a bit rough.
Ive read about it that i can take it to plane . But my question is Unboxed. Because one of my friends wants one and i bought it from Amazon and i dont want to unbox it
If you left it boxed (which you said you'd prefer) then it's likely it may be looked at as bought duty free overseas and when brought back into most countries, they may apply local taxes / duties.
If you purchase it online for delivery locally in Germany, then it's likely your home country (which is ?) taxes etc would not be applied, but maybe local German taxes / duties will be.
You could get 2 hits on this.
I would just hunt down a great deal locally, wherever you / your friend are based.