What does da mean in Chinese using 4 tones?

You should know that for any given tone, there might be multiple Words, each with different meanings. Even a Word would have different meanings. Here I list the more common ones.

Da (first tone)

搭 noun - befitting

verb - commonly used with 巴士 meaning "take the bus"

Da (second tone)

答 noun and verb - answer

达 verb - to reach (a destination, target, goal)

Da (third tone)

打 verb - hit. But also used with 电话 meaning "to call", though literally it would mean hitting the phone, it actually means to call using the phone。

Da (fourth tone)

大 adjective - big. Also used to describe seniority.

Take note that some of these Words, when paired with another, may have a meaning not stated. 发达 used together, for example, would mean to prosper/get rich. Which is a totally different meaning from the general 达 used alone.

Chinese is complicated as a language.