In French, words spelled with just “u” use a different sound than those spelled with “ou”. “ou” (in la Métropole) is similar to the sound in English “do”/“too”/“sue”/“shoe” etc. while “u” is similar to Standard German long “ü”/“üh” like in “Lüge” but the German one is relatively reduced and isn’t quite as frontal/strained/constricted.