The Bayern Munich striker worked under Klopp during his time at Signal Iduna Park.
The Polish striker represented Dortmund for around four years during which Klopp also served as the manager.
Lewandowski revealed that two-hour chat with Klopp helped him overcome early struggles at Signal Iduna Park.
The 32-year-old said,
“The first three months at Dortmund were difficult.
“But I still know exactly when the situation got better.
“We lost an away game in the Champions League in Marseille. At the time, I didn’t really know what my position was with the coach.
“After the game, I talked to Jurgen Klopp and asked him openly what he expected from me. We spoke for almost two hours.
“I told him what was on my mind, and he explained to me what he expected from me.
“After this conversation, everything worked better. We won the next game 4-0 against Augsburg, I scored a hat-trick and got an assist.”
Lewandowski signed for Dortmund’s arch-rivals Bayern Munich in 2014 and has since established himself as one of the best strikers.
Elsewhere, Jurgen Klopp was snapped up by Liverpool in 2015, and the German manager’s cabinet is now filled with a Premier League trophy and Champions League title.
Lewandowski has been on a different level in the past two seasons, particularly after the arrival of Hansi Flick as Bayern’s manager, racking up goals in numbers.