PSG were dominant so do not need to change tactics. They can win the game in England if the play the same way. PSG deserved to win they had 27 shots on target. Liverpool had 2 but scored against the run of play.
Liverpool itself played like it was not their usual playing style. I don't know what happened and why it happened that Liverpool played that badly. Liverpool's defense line even continuously managed to get past PSG's front players. And yes, even though PSG lost this match, I really appreciate their game which managed to dominate the match very well. they are just unlucky because Liverpool has an extraordinary goalkeeper. And this match is similar to PSG vs Liverpool Goalkeeper. 
Liverpool were just lucky enough to win this match with a fairly unexpected good counter attack and Elliott made good use of it. In the second leg, if Liverpool continues to play as badly as in the first leg, PSG could turn things around. but I hope Liverpool will continue to play with their usual strength. So we can see two strong teams attacking each other in a more balanced manner. So the match will be exciting.