Tell your classmate that you have done a lot of things today. In fact you are extremely busy.
Try to use 可...了 and 其实。
我今天作的事可多了，其实忙得不得了。
[Comments]
Click on the Chinese to hear the sentences spoken.
Alternatively one can say 我今天作的事多极了,真是把我忙给坏了or 我今天作的事多得不得了，真是忙极了。