Something like that. Or На углу стоит здание.
To assist your learning, we differentiate between "sentences" and word combinations that might be a part of a sentence. Sentences will start with a capital letter and end with terminating punctuation:
- это молоко = this milk
- Это молоко? = Is this milk?
- не то молоко = wrong milk
- Это не молоко. = This is not milk.
- пять человек = 5 people
- Девушка дома. = The girl is at home.
As much as translating "real" sentences is fun, some finer grammar points are best addressed with short phrases that have all irrelevant variables removed.
My teacher told me "на углу" would be on the external part of the corner, while "в углу" is the internal part. Is that right?
I think you're right. To me, на углу is like the corner in a street, in the city, and в улгу is the corner inside a house, thus, the internal part.