Berlin S-Bahn: advice in English

I see a lot of discussion here with regards to Berlin S-Bahn, but sadly my German is not so good to be able to understand more complicated discussions and Google Translate can only get you so far :).

I am looking for advice/tips on buying an Add-on for TSC, keeping in mind that I am purely interested in playing the Berlin S-Bahn maps.
I have the Mitten durch Berlin, Ringbahn and the BR481 Add-ons, so I am now looking at buying the Szenariopack vol. 1 or Szenariopack vol. 3 by TTB.

I have seen the Strassenbahn project by Mumpfi, but I have been unable to figure out how to make it work since it is all explained in German and as far as I could tell it requires a large amount of Payware for the track to work as it is supposed to?
I have also seen certain Youtube videos, which involve the S-Bahn lines going to the BER Flughafen, so I was wondering which Add-on would be needed to play that? Right now the Berlin-Leipzig Add-on is on sale on Steam. Would that involve the section of Berlin from the airport/Königs Wusterhausen to the Ringbahn?

Bottom line is, any recommendation for Add-ons that would allow me to play as much of the Berlin map as possible will be highly appreciated.
Thank you guys!

Thank you both for your responses!

SÜWEX if I understood correctly, I would need every DLC listed in the ReadMe for the track to work? That is unfortunately a big investment to get into at the moment, so I don't think I'll be getting them :/.

bahnjan are you referring to the Berlin: Havel - Spree - Dahme thread? If yes, I have been keeping up to date with all of the posts there.
Nice to hear there'll be more info soon!