The German ü sounds like the "u" in English "tube". Say "ee" (like in "see") but round your lips like you're about to whistle — that's the ü sound. It's the same sound as the German "y".
Same sound as "y" in German
The ü sound is identical to the German "y" (as in Typ, Gymnasium). The umlaut shifts the "u" (an "oo" sound) forward in your mouth to become "eww". You'll see ü in many plurals where the base word has "u".
Hear the "eww" sound
English
tube
the "u" here is close to ü
French
rue
French "u" = exact same sound
How to
say "ee" + round lips
= the "eww" / ü sound
Hear the difference: u → ü
Read both words aloud — listen how the deep "oo" shifts to the forward "eww" when the umlaut appears.