Marmoush, back from Egypt's AFCON campaign, struck in his first game back on Saturday.
“It is important to score a goal and help the team,” said Marmoush in an interview after the game.
“I am very happy to be here after AFCON and help my team. I saw that Matheus (Nunes) broke through and it was a good finish.
“I’m happy for the goal and happy for the three points.”
Meanwhile, City manager Pep Guardiola said of his striker: "Last season when he arrived for three months he was unbelievable; without him it would not be possible to qualify for the Champions League and reach the FA Cup final.
“He’s a special player, not old ,not young but he has margin to improve. His dynamic energy and runs are really good.
“I see him more as a striker not a proper winger. He’s a guy for transition actions.
“I am so happy for him. He arrived clean after AFCON, and I am so pleased for him.”