The visitors came from behind to win 2-1 thanks to Mohamed Salah's successful penalty.
Gomes later said: "A tough defeat according to what we did in the game. We started well and we were a bit unlucky suffering the first goal, but we responded immediately in the first half.
"We were not paying attention to some details. We deserved something from this game - at least a point.
"All the details count especially against the big teams. If you do little mistakes they will make a goal and we will suffer."
On the penalty, Gomes said: "Straight after our first goal, but these are the small details. Suffering again from the penalty is tough - we tried to go again. The game is finished and we did everything we could."
"It is not easy, but it is a matter of time.
"We are not in a good phase, but we have to stick together. We have had tough defeats against big teams but we are going to keep fighting and we have a lot to prove.
"I ask the fans to stick with us as we are going to keep improving."