To say before, you can either say 之前 or 以前: i.e. 我畢業之前。。。 (before I graduate) 她以前是老師。。。(she was a teacher before) 事情發生之前。。。(before something happen)

Bi4ye4 yi3qian2...shenmeshenmeshenme

~之前

before = 以前 = yǐ-qián before I graduate = 我 毕业 以前 wǒ bì-yè yǐ-qián