One night in Peking

It's the last night that I stay in Peking. I am going back home tomorrow, finally!! ^^

It's a little awkward to say "It's the last night..."  What you mean to say is "Tonight is the last night..."  今晚是我留在北京的最後一晚。 Also, you would want to finish that phrase by saying "that I will stay in Peking."  This is because you haven't stayed yet!  (這還是屬於未來的事情！）

北京很棒。 雖然人多，但是地方熱鬧。