I made like conversations, I hope it could help. In these Q/A you can understand the difference between every sentence, I ask you to not try to understand a languages by another or by translation, it's an universal advice that we hear all the time from teachers but I am not a teacher !!
Q : What's Mustafa?
A :
Mustafa (is) a man =
مصطفى رجل
Q : Who is Mustafa?
A :
Mustafa is the manI am talking about مصطفى هو الرجل
Q : Are you talking about Mustafa the man or Mustafa the name?
A : I am talking about
Mustafa the man =
مصطفى الرجل
هو is translated "is" in the sentence, because it can have the meaning of "is", and about THE :
ال+رجل = THE+man
Your questions are welcome
