Hi ^^

It's raining outside ! I'm staying in my room in front of my computer!
=> I don't know why, but I'd say "in my room" before "in front of my computer"... :D

Browsing the web with no intentions ! I was aroused by my claasemate at 7:20 .
=> My classmate woke me up at 7:20 am.

After rinsing and buying two dumplings(包子) ！I had four classes in the morning and none in the afternoon ! I had a rest at noon ! That's all !

Ok, that may be a silly question haha but when saying "after rinsing", what are you talking about? Did you rinse the two dumplings you bought or do you mean "wash"?
If you wanted to say that you had a shower or something like that, I think you should use "wash"...