I don't know if I should chase or how to chase a girl.

Loulou, if you and that girl are not in the same city, I suggest you don't chase her. If you really like her, go after her boldly! Man! That's the question 1. Question 2: If it is really the landlord who "jokingly asked my sister if it is possible", summon up courage to ask her if she would like to. The possibility of landlord and sister is quite high. Here comes question 3: In fact, you can come straight to the point and explain directly. If not, then keep chasing. There is also a gentle board. If your sister works late at night, you can buy her snacks. Every day, happy every day Ahem. . . . Finally, it depends on the landlord's own sense of reality.