I am a Taiwanese currently living in HK.
If you like nature, I would recommend you 昂坪360 Ngong Ping 360 in 東涌 Tung Chung (which is also a MTR station). There is also a huge buddism statue on the top of the mountain, and sometimes they may have some martial arts performance there. 大澳 Tai O is also a great place for people who likes sea, pink dolphins, and traditional houses built just above the tidal area.
The most important phrases in Cantonese you must know is 唔該 (ng goi) which means 'excuse me', 'thank you', or when you want to catch waiters' attention in a restaurant.