How long does it take to master chinese language?

Here is my situation, i am an english speaker and studied chinese for just eight months and now i am taking my biology course in chinese at the university. this is real crazy that most of the time i think i am not studying enough to master chinese as fast as possible cos this language is complicated with so many characters and you meet professors with different accents of which some of them speak local languages. i can understand 60-70% in subjects like Zoology and botany but when it comes to chemistry is a problem, i can't just understand anything and most of the time i get headache. do guys think i am lazy and need to study hard? ya i can speak pure chinese now but listening is still a problem and of course i can write chinese but not as fast as the chinese.