To be honest, unless you are sure of your English, I wouldn't try to be funny in messages. When you are speaking to people,you can because if you see that you said something inappropriate, you can fix it. It's just not the same in writing.

English is a hard language because we use idioms ( a group of words that together do no usually have the same meaning when each word is alone For example , if someone says that something that costs and arm and a leg they just mean that it costs a lot of money. A piece of cake usually means that something ( a job or a task) was very easy. Just try and be yourself! If you can, read American authors. You will pick up some language there.