1、I tried so hard in spite of the way you were mocking me
接着后面一句话,意思是：尽管你一直这样嘲笑我,我都努力尝试.
2、One thing,I don't know why,It doesn't even matter how hard you try.
此句完整变换是One thing,which I don't know why,is that how hard you try doesn't even matter.
这里的I don't know why作定语修饰one thing,而It做how hard you try的形式主语,可变为how hard you try doesn't even matter,而is that之后所指的就"我不明白的那件事".
顺便说一下,有很多英文歌曲为了唱起来押韵,它们的歌词有些句子的成份是不完整的,所以大多歌词个人觉得并不是学语法的好材料.