The Midlands club battled hard to get a dramatic 4-3 win on Tuesday afternoon.
They beat RB Leipzig’s youngsters in a mirror of the fixture played between the senior teams.
Post-game, Gambau said: “We are so happy. We won the game which, away (from) home, is not easy, and we can go through to the next round.
“We are very happy for the boys. It is well deserved to go through, because I think we are growing as a team. Happy with the result today.
“They are happy. It is a big win that brings us qualification to the next stage.
“It was a must-win game, because if not, we do not go through. The way we did it, in the last minute, it’s time to enjoy for them. I am happy with the performance of the team.”
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