I pretty understand it confuses you a lot. It's related to the Korean culture more than the language itself. '우리' refers to either 'our' or 'my' in english depending on the context and the relationship. It is often considered as 'my' in spoken language. Koreans expand the concept of 'I, my, me' for sharing. This sharing culture can often be found in many cases. For the instance of a meal table, Korean people share side dishes in the middle of meal table while all the food are put on an individual own plate in other culture. ( As I know, it's quite unique eating culture. It sometimes doesn't look good to foreighners, but it's our culuture.) For example, '우리 아버지' refers 'my father'. Our father does not quite make sense when you talk with your friend. However, it expands unlogically. So, you are expected to treat your friend's father well like your father. however, '우리 학교' could mean two cases: either 'my school' or 'our school' meaning that we go to the same school. When you talk to your friend going to the same school with you, it means 'our school' while you do to your friend going to the different school, it means 'my school' It really depends on the context and relationship. In summary, it cannot be shared, it must mean 'my' in English(우리 아버지). When it can be shared, it could mean 'our'. Good luck. ^^

우리 means we.in mandarin,usually use our or our family's someone to express more endearment or to expess the relationship is more tightly than others.so korean is the same.