In case anyone had any doubts about whether BER's design capacity of 27m pax would cope... Berlin's 2 airports saw 34.7m pax in 2018. Furthermore Jan 2019 saw an increase of 400k pax compared to Jan 2018, so on a rolling 12 months it's now 35.1m pax
If BER were to theoretically open tomorrow and SXF continues to handle 12m pax (with which it really struggles) then BER would be running at 85% of design capacity from day 1. The new extension to BER is essential