I’m excited when I am doing some difficult problems.这句话有什么问题

I’m excited when I am doing some difficult problems.这句话有什么问题 what I'm doing 和 what am i doing 有什么区别? i'm happiest when i'm with you这句话有语法问题吗? i am just doing some stuff是什么意思? I am excited when …… I am angry when…… I'm doing some work down at local library.这句话中用的down是什么意思啊? i am married with tom 这句话有问题吗 I am excited fall asleep. I am just so excited! The news exciting,I am excited.这句话好奇怪啊 i think study english is very difficult.这句话有问题么?快来救命啊, 有句歌词：i'm strong when i am on your shoulder,这是什么歌?