Thank you BBQ,
ok hareem
noitce that.
1-4 are both on the shoulder. Infact 1 covers most part or the shoulder.
In order to tune/build them,
1= All pulling exercises. Including chinups/ pulleys dumble pulls (you could do it at home)
4= pressing exercises. shoulder press(you lift weight up- over the head) , some what push ups.
2= Triceps, dumble extension I guess reha’s video had them,
3=dumble curls.
5= I mostly will build it self while you are working on other exercises.
Now all those parts compose the shape of the arm.
Good news is more parts means more area to improve 
LP: for fats 
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