Chinese is a topic-prominentlanguage, which means that the topic (what the sentence is about) comes at the beginning of the sentence. A topic is roughly equivalent to the X in the English expression “As for X, …”. (1) and (2) show how topics come first in Chinese sentences.
(1) Zhāngsān wǒ yǐjīng jiàn – guo le
Zhangsan I already see GUO LE
Zhangsan, I’ve already seen (him).
(2) zhèi – kē shù yèzi hěn dà
this – classifier tree leaf very big
This tree, (its) leaves are very big. (Li & Thompson, 1989, p. 15)
In (1) and (2), Zhangsan and the tree are what the sentences are about, hence they appear at the beginning of the sentence.
Li, C. N., &Thompson, S. A. (1989). Mandarin Chinese: A functional reference grammar. Univ of California Press.