The ringing sound you hear in all of the phone calls which are made in the whole season are wrong. The German ringing (and waiting) sound has regular intervals, a different tone and each sound is longer in general. While this would be acceptable for the CIA phones (which may use a US carrier and be dialing to a US number) a German phone calling a German number will always make the German connecting beeps.
After the meeting with the Germans at Restaurant Grosz it looks like Saul walks to Gendarmenmarkt. We have to assume he took a taxi because Grosz is on Kurfürstendamm in West Berlin, whereas Gendarmenmarkt is about 5,5 km (about 3,4 miles) away in East Berlin.