if i were you and my behaviour could decide(influence) whom you are going to be,what am i gong to do now
没必要加now（第1个其实第2个也没比要）,句意更加通顺,加语气词could顺便表时态（因为现实你并不能影响他）另外我的行为会影响他可能句意更好更通顺,没有比要弄个主语从句）.i will be how to do不是疑问句,并且是中式英语,完全按字面顺序翻译.
if i were you and what i do could decide who you will be,what am i going to do.(如果用how,就要用how am i going to do it,但是不知道it指代什么,所以最好用what)