Liverpool was really pressed hard by PSG in the first half because PSG was able to control the game well and launch many shots. Liverpool's defense line was so strong and they had to try to kill the movement of Dembele and Kvaratskhelia because they managed to create a lot of pressure in the first half.
In another match, it seemed like Barcelona had a big problem in this first leg because Cubarsi's red card certainly made them lose their stability of strength. Even so, Barcelona managed to defend well in the first half and the score was still 0-0. We will see in the second half whether Benfica will be able to score a goal because currently they have an advantage in the number of players.
I think the main reason Liverpool haven't lost yet is not the defense but the goalkeeper. It will be interesting to see if he can continue like this in the second half and if Liverpool can move the game away from their goal. So far everything is going as I expected but it is not reflected in the score. Everyone was too enamored with Liverpool and this distorted the perception of their real strength.