why are some comedians really funny? is it an inborn talent?

All I know is what I've heard them say. It's partly talent but's it's also a skill that you need to develop in front of an audience, finding out what works and what doesn't, and part of that learning process is the nights when nothing goes right and the audience heckles or ignores you.

You are not a doctor. 

Snitch

Snitches are sent by witches who fall in ditches and later get stitches and then never get batches.

Dylan: Frick that kid, he trucking told on me again 

James: Yeah, he must be a mothertrucking snitch

I dated one, a well known, noted comedian from NYC.  He knows Amy Schumer and Dave Chapelle.  HE WAS TOTALLY NUTS.  He is great on stage, but off stage, moody, miserable, depressed. angry.  So crazy that those two personalities somehow collide...  

You must like little boys.

what do you mean and what country did you come from

I'd say it's mainly a natural talent, partially derived from a lot of negative experiences in life that their natural gift can make light of to make others laugh. Most comics come from very bad childhoods, or have other issues in life they're dealing with. Take Robin Williams or Steve Martin for example. There's also a big variety of comedians; stand up, sketch, even radio personalities can be considered comics. Jimmy Kimmel for example was a long time radio show host before he migrated to television. I too was a local radio "comic" writing and producing numerous commercial parodies and coming up with spur of the moment one liners to ad-lib in my shows.

Some comics are funny enough to write their own material, others require writings and they just execute the humor. An example of that would be Alec Baldwin either on SNL or Match Game. You can tell he's reading off of a teleprompter. I find personally that those who write their own materials are the funnier ones as their delivery is a lot smoother in nature and when they do ad-lib they know just what to say, how to say it, and when to say it. Either way I'd say a good part of it is inborn talent - just as you have an inborn talent for being highly educated.

I think you either have it or you don't. But it also takes practice.

Oh! My Goodness yes. You either have it or you don't.

I don't know if this can be done?