The Poland international played his final home game at Signal Iduna Park on Saturday, ahead of his move to Bayern Munich, as Dortmund beat Hoffenheim 3-2.
Lewandowski was presented with gifts from the club and received a standing ovation from supporters when he was substituted late in the match.
While he will end his four-year spell with Dortmund at the end of the campaign to join rivals Bayern, the 25-year-old is determined to secure a Bundesliga triumph at Hertha Berlin and victory in the DFB-Pokal final - which also takes place in the German capital - against his future employers before departing.
"I'm still a Dortmund player and my focus is on these two games in Berlin. That's the most important thing for me right now," he told the Bundesliga website.
"I've learned a lot here in Dortmund and I know that I'm a better player now than I was four years ago, but there's still a lot of football to be played. It was my last game in Dortmund but we still have two more matches to play in Berlin.
"These have been four fantastic years for me at BVB and they're not over yet. I've scored a lot of goals and experienced so many great moments here, both in the Champions League and in the Bundesliga.
"We won the league twice and hopefully we can win the DFB-Pokal twice as well. My story here isn't over yet."
Lewandowski sits joint-top of the Bundesliga scoring charts on 18 goals along with future team-mate Mario Mandzukic.
The former Lech Pozanan striker is eager to finish as the league's leading marksman but insists it is not the most important aspect of his season.
"I don't want to put myself under any pressure," he said.
"If I am top scorer at the end of the season, that would obviously be great . But it's harder to do that if you put extra pressure on yourself."
