Despite the one-sided scoreline, Porto finished the game having had 45% possession, won six corners and weighed in with eight shots, three of which were on target.
"Honestly, it was not an easy game even if we scored five," Mane told BT Sport. "We played great football from the beginning to the end.
"I've always enjoyed playing with these great players. Without the team [behind us] though we are nothing. They give us the ball."
Liverpool host the Portuguese giants in the return leg at Anfield on Tuesday, March 6.