why is yahoo answers shutting down on april 20th?

Because Verizon Media is choosing to shut it down (just as they did Yahoo Messenger and Yahoo Groups). No specific explanation was given, but considering the significant decline in quality of content on the site versus the cost of cleaning it up and keeping it running, it's not a surprise (a disappointment, but not a surprise). 

New laws are coming out that will hold social media sites responsible ( libel) to clean up what is posted ( racism. slander, abuse ,porn etc...FAST or face fines = $$$$$$$$$$$

This website is a joke.

You got it all wrong. April 20 is the last day you can post Q&As on Answers. It will then revert to a read-only site for the next two weeks before its shutdown on May 4. More on that can be read here: https://help.yahoo.com/kb/SLN35642.html