why we add 으로 and 러 to the verbs ???????
hi ,
in this sentence 그는 어디로 가고 있습니까 ? why we said 어디로 not 어디에 ???
and in this sentences 그녀는 (해변으로) 가고 있습니다
나는 7시에 ( 일하러) 갑니다 why we add 으로 and 러
do you can explain ???? is there a diffirence between 으로 and 러 ???

Question

why we add 으로 and 러 to the verbs ??????? 
hi , 
in this sentence 그는 어디로 가고 있습니까 ? why we said 어디로 not 어디에 ???
and in this sentences  그녀는 (해변으로) 가고 있습니다  
나는 7시에 ( 일하러) 갑니다  why we add 으로 and 러   
do you can explain ???? is there a diffirence between 으로 and 러 ???

Answer

"-로" is used to put an emphasis on "direction" while "destination" is stressed, then "-에" is used rather than "-로"
해변으로 = in the direction of 해변
해변에 = to 해변(focused on 해변 itself as destination)

"verb + -(으 or 하)러" is totally different from "noun + 로" and "에".
It means "in order to do something".
나는 7시에 갑니다.
where? ☞ 직장에 = to my workplace(your destination)
for what? ☞ 일하러 = in order to work(the reason why)

\^o^/

Answer

As you know, 어디로 is 'where' 'where to go' 
(place)~로, ~으로
So, 해변으로 is correct.
ex) 도서관으로(to the library), 학교로(to the school), 방으로(to the room), 버스정류장으로(to the bus stop), 쇼핑센터로(to the shopping centre) and so on.

~하러, ~러 is doing something.
일하러 is correct.
ex) 마시러(to drink), 자러(to sleep), 걸으러(to walk), 수영하러(to swim), 운동하러(to exercise) and so on.