1.They are interested in/keen on/fond of the film.(be intersted in=be keen on=be fond of+N/V-ing)
2.Despite being old,she works hard.(despite+N/V-ing)
3.We used to cycle to school two years ago.(used to+V-inf)
4.It is about 100 km from Ha Noi to Hai Phong.
5.If you aren't careful,you'll have an accident.(if 1)