Before and after can be expressed using 之前 (zhīqián) and 之后 (zhīhòu). They are in relatively the same vein as 以前/以后, except that these two are adverbs, while 之前/之后 is a preposition. Don't forget that these two are talking about before and after in terms of time.
Structure
Examples
Lái zhōnɡ ɡuó zhī qián, wǒ de hàn yǔ shuǐ pínɡ hěn chà.
来 中国 之前 ，我 的 汉语 水平 很 差。
来 中国 之前 ，我 的 汉语 水平 很 差。
Before I came to China, my Chinese was bad.