I have the same problem with Spanish comedies.  The problem with comedies is that much of the humor relies on context which a person from another country might not be aware of.  Also, when I watch a drama if I miss a word here or there I can still understand what is going on.  With a comedy, if I miss a word, I do not get the joke.

My solution lately has been to watch comedies with my teachers or language partners and have them explain the parts to me that I do not understand.  

I think comedies require a higher level of language ability and a higher level of cultural awareness than other videos do.  Today, as my Venezuelan teacher was explaining things to me in a Venezuelan comedy, he told me that he had watched alot of American TV and could get the jokes in American comedies. However, he watched a British comedy and even though he knew the words he did not get the jokes. 

Several months ago a language partner recommended a particular comedian to me.  The comedian speaks rapidly and it was just too hard for me to understand.  Every couple of months I search for a video from this comedian again and see how much I can understand.  I still do not get all of it, but I get more of it.

My advice would be not to worry too much if you do not get the jokes.  If you enjoy watching the show, go ahead and watch it.  If you do not enjoy it, put it aside for awhile and watch something that is easier to understand and come back to it weeks or months later.  However, do not worry if some of the jokes do not make sense to you.  Some of them would be jokes based on things only someone very familiar with what was going on in the U.S. at the time the show was made would understand. 

Hi Yuki. Friends is a great show. It's one of America's most popular shows, and it still plays on TV today.

American shows tend to make fun of situational irony. This means that characters are often placed into situations that are embarrassing or distressful, due to coincidental circumstances that the characters themselves usually create. Lots of Americans find this funny.

American humor also uses insult humor and slapstick humor. Insult humor is when the characters are being insulted. Slapstick is humor based off the characters going through some physical harm or accident, which usually depicts their clumsiness.

A good way to notice if something is funny is to try to search for the coincidences that occur to the characters. Usually that means that it is meant to be funny.

Sometimes, American shows play on this expectation and create logical inconsistencies, which are funny as well. But look primarily for coincidences at first, since that is what many American shows use for humor.

I hope this helps.