can you say me how to express that i am laughing?
i dont know how to say that i am laughing or what you said was funny, for example "LOL"

Question

Answer

"Stop it you're killing me!" Is a common one in spoken English. 
The day people start actually saying 'LOL' I in daily speech I will give up on absolutely everything.

Answer

Well, similar to LOL, there is also ROFLMAO which means "Rolling on the floor laughing my a** off".

Or you could just write haha (similar a jaja)