Apart from wanting to find new challenges outside of the Bundesliga, Lewandowski goal is to come to Barcelona to add to his trophy collection with a different club. Lewandowski experience made him adapt very quickly to Barcelona, he also immediately became Xavi mainstay in Barcelona attack line. The Europa League trophy is still Barcelona priority, Lewandowski is very motivated to win his first trophy with Barcelona.
It is not true. If Lewandowski wanted to hunt for trophies, he would choose other clubs that were not in crisis like Barcelona. He had many options I believe but in one interview, he said that he admired the football style in Barcelona that is why he joined them.
He admired the football from Pep Guardiola and wanted to experience tiki taka at where it was born, Barcelona.
The age factor don't hinder Lewandowski's ability on the field in the slightest, he can still play for 90 minutes without any complaints. Of course Barcelona can't count on him much longer in their squad due to the age factor, as long as he can still make a good contribution to Barcelona, Xavi will continue to rely on him despite his old age.
He is younger than Messi and Ronaldo and with his professional training and his intention to take care of his body to prolong his career, he will not have problems with age factor in coming two or three seasons. Lewandowski is a different player than Ronaldo and he does not run much, does not rely too much on his speed like Ronaldo.