The 25-year-old completed a 125 million pounds ($169.46 million) switch from Newcastle United to Liverpool on transfer deadline day, bringing an end to a transfer saga that had dragged on throughout the close season.
"It's great that everything was settled before the camp and that I could focus on playing football again," Isak told Swedish media after the defeat in Pristina, where he came on as a second-half substitute.
"It's been a fairly new situation for me, but you always learn and develop mentally off the pitch as well."
Isak had made it clear he wanted to leave Newcastle at the start of the window and played no part in the club's pre-season or opening league games, accusing the club of breaking promises and misleading supporters.
"Obviously, not everyone has the full picture, but that's something for another day," Isak said.
"I can't control everything that's said or written. But I'm happy that I became a Liverpool player."