Mandarin

Lesson 19

• 我学汉语学了五年。I have 5 years of experience learning mandarin.
• 我学汉语学了五年了。second le indicates that the action is still taking place (I've been studying since 2015)

你要听多长时间（的）音乐？Only used with non pronouns. Otherwise, 我（学）汉语学了五年。

Joining two actions. First says how you did the second.

• 你怎么上去？我坐电梯上去。

hao means finished, as resultative complement.

• 写好信。画好画儿。

来 + verb. Purely optional word.

• 我来介绍一下。

x + 来 + x + 去。 Back and forth.

• 游来游去。
• 走来走去。

Lesson 20

又 VS。再

• 又 is for again in the past
• 再 is for will happen again in the future