ممكن شرح الجمله دى وحلها
 

the too short young man cannot join the police
: (If)

معناها القزم لا يستطيع الالتحاق بالشرطة
و لو انت سؤالك Re - Write :- باستخدام If

هتبقى If He Was Taller (than now) , He could join the police

If he weren`t too short ,he could join the police .

جزاكم الله خيرا

Firstly I do not know why all here typed the sentence in the past form! the tense is the present as it's a truth
The answer will be

If you are a young short man , you can not join the police