"We didn't deal well with some details in the first half and conceded many errors," added the Chinese international.
After the restart, Bayern had a perfect start to the second half as Chris Richards' square ball into the area allowed Lewandowski to drill the ball from the edge of the box into the top left corner with 51 minutes played.
Also on Saturday, fifth-seeded Stefanos Tsitsipas earned a spot in the fourth round after his Slovenian opponent Aljaz Bedene retired from the match and hobbled off the court when trailed by 6-1, 6-2, 3-1.
"With 53 points you cannot win any game," admitted Shanghai coach Milos Paden.
China's Shi Yanghe and Zhao Jiangqiong won the men's and the women's 65km races respectively.
"I think I played a really good match. I was very aggressive. I knew from last year I had to change something, so I really wanted to be better than last year and definitely, I was today," said the world No. 2.
The league's governing body is therefore inserting one match into each round that was initially scheduled for a later date.
Clinching a victory in his 100th match at Roland Garros, the record 12-time champion secured a place in the last four for 13th time in the clay major, ending an impressive run from Sinner who had upset 11th seed David Goffin and 6th seed Alexander Zverev in his previous matches.
Meanwhile Barca loaned 20-year-old left back Joan Miranda to Betis, while Rafinha Alcantara was sold to Paris Saint Germain for a bargain three million euros and central defender Jean-Clair Todibo (who is not in Koeman's plans) was loaned to Benfica on a two-year deal.
The club said that four outfielders and three infielders have been infected with the virus, as well as four non-playing staff, bringing the total number of recent infections at the club to 13 after it was revealed on Sunday that right-hander Daiki Iwashita and a staff member had tested positive.
Facing Tianjin, Jiangsu set the tone in the first quarter with a 29-7 run, letting its reserves finish off a 106-59 win.