45 minutes with checked luggage is impossible, unless your incoming flight is (very) early. With cabin luggage only, you might make it if you have printed your boarding pass OSL-TXL. In that case you must use the direct channel for connecting INT-INT passengers before taking the escalator down to the arrivals tax-free shop/ luggage belts. (It is about halfway down the long landing from passport control to the down escalator). Have you checked the flights OSL-TXL on SK or the flights OSL-SXF (Berlin Schönefeld) on DY (www.norwegian.no)? They might offer you more doable connections than your impossible dream!