Baltogs orange/blue

I had a very sketchy plan of where I should go, as I this time did not have a map of Berlin, but I tried to remember the route I had been walking four years before. And it was something like walking west from the Grunewald railway station, crossing the Teufelsberg hill and reaching the river Havel after about an hour and a half, then turn to the left and follow the river to a small spit of land. And turning left again I should return to the railway after another hour and a half.