An early penalty converted by the Nigeria striker earned Gala a deserved 1-0 win.
Osimhen said at the final whistle: "My team-mates and I managed to defeat a very good team by giving it our all. As Player of the Match, I'm very happy, but this is a success for all of us, along with our coach Okan Buruk.
"Our fans are incredible, as always. We've shown our true strength at this level. We've proven to the entire public what warriors we are. Whether it's here or on any field, as long as we play like this, we'll win every match."
Meanwhile, Gala midfielder Ilkay Gundogan also stated: "It feels very special, especially coming from a bad defeat in our first game of our Champions League campaign. Playing against an amazing Liverpool team, we knew it was going to be very tough and that we needed a special team performance, and convert the chances that we got. That's exactly what we did.
"Sometimes, in the game, you cannot control everything because the opponent is so strong. It was about defending together and suffering together through periods of the game. This makes this performance even more special. We are all proud to be able to beat this Liverpool side.
"Congratulations to all my team-mates. We played like Galatasaray this evening. It was a crucial test to demonstrate our strength. We face very tough and strong teams at this level. This match gave us great confidence."