Omar Marmoush is Manchester City’s most important signing since Erling Haaland.The Eintracht Frankfurt forward spent Tuesday in the north west undergoing his City medical ahead of a £60m transfer that is set to be announced before his new team look to lay down a marker in their pivotal Champions League clash with Paris Saint-Germain.City regard this deal as a significant one, “ticking every box” as they look to fast-track a new era at the Etihad…