"We are exhausted from a very intense game but in moments of like this, I struggle to find the right words, to express my respect for the boys," Klopp was quoted as saying by ESPNFC after leading Liverpool to their first Club World Cup title.
"It was incredible, we did so many good things, everyone was on the edge pretty much and there were so many sensational, good performances," he added.
"Late goals we don't want to need them but they were necessary and important. The boys have improved a lot over these months and when you start believing you believe through the full 90 minutes and in this case 120 minutes," Klopp said.
Firmino, who scored an injury-time winner against Monterrey to send Liverpool into the final, did it in one more time as he netted in the 99th minute to hand his side the title.
Liverpool, the Champions League reigning champions, became the second English side to win the tournament, after Manchester United in 2008.
Flamengo coach Jorge Jesus said he was proud of the performance his team provided.
"We shouldn't forget that Liverpool is the strongest team in Europe and we were equal to Liverpool and didn't face particular problems in the first 95 minutes, indeed we could control the match for many stretches," Jesus said.
"But two big teams faced each other and at the end of the day I am very proud of my players and their performance," he added.
( With inputs from IANS )