N서을타워

우리는 N서을타워에 갔어요. (This is a very good sentence. How about writing like this? 우리는 N서울타워에 올라 갔어요. I just add '올라'(climb up or go up to)
We went up in the tram and bought a ticket for both ways but it was so crowded and the mountain isn't that big so we decided to walk down.
남산 공원에서 길을 잃었지만 아름다운 밤이있어서 괜찮아요. 

This is also very good sentence. If I have to correct a part, I would like to do with ~아름다운 밤이어서 괜찮아요. Actually 아름다운 밤이 있어서 sounds very very peotic and lovely expression and even ordinary Koreans like me can't make this beautiful expression. Whether you intended or not, it's beautiful. ^^ 

N서을타워

우리는 N서을타워(남산(南山) 서울 타워)에 갔어요.
We went up in the tram and bought a ticket for both ways but it was so crowded and the mountain isn't that big so we decided to walk down.
남산 공원에서 길을 잃었지만 아름다운 밤이있어서 괜찮았어아요.