trackpad is not working as it should!

My Mac's trackpad (Mac Book Pro 15", 2010 or 2011) is not working as it should. Sometimes it makes a selection, although I don't want to do that. It is hyper-sensible although I configured slowly. And it does not click at all. Even ticking is sometimes a problem. I have shut down the system already a couple of times, but that does not seem to help.

Anyone any idea what is wrong and how to solve this?

Your help is much appreciated.