What is the strangest thing you have ever done when you feel exhausted?

Please correct my sentences. 

Yesterday I talked to my friend on the phone and somehow our conversation went to a weird topic.

The topic was,  that “What is the strangest thing you have ever done when you felt exhausted?”

In my case I always feel exhausted when my classes are over.

One day when I got home from school, I somehow tried to put a bus ticket into the lock instead of a key. I don’t know the reason why I did it but it happened.

There is another story that I have to tell you. When I get tired I sometimes have watch exactly the same dream that I somehow teach a bunch of Predators (from a very well-known movie) international politics which is my major.

Since it always seems like they are keenly eager to learn about China, I teach them about when The Qin Dynasty had finished, why the Chinese government has put censorship on its people, and how the China used military force to take over the Spratly islands and so on….

Anyways …, if you have ever done something funny or interesting when you were tired, please write it down and share!

Your English is very good. The only errors I see are : 

"When I get tired I sometimes watch exactly same dreams that I somehow teach a bunch of Predators (from a very well-known movie) international politics which is my major. "

I would write : " When I get tired, sometimes I have the same dreams where I am teaching a bunch of predators (from a very well-known movie) about international politics, which is my major".

Another error I see is : " Since it always seems like they are keenly eager to learn about China, I teach them when Qin Dynasty has finished, why the Chinese government has put censorship on its people, how the China uses military forces to take over Spratly islands and so on…. "

I would write : " Since they always seem to be keen and eager to learn about China, I teach them when the Qin Dynasty has finished, why the Chinese government has put censorship on its people, how the China uses military forces to take over Spratly islands and so on…. "

All in all, only minor errors.