I believe it is time to have a certified arborist clean up your tree. The branch you show me has mushrooms growing on it. That is never a good sign. They usually indicate internal rot. Just because some branches are dead does not mean the entire tree is in trouble but an arborist would be able to evaluate your tree and let you know. If it just some dead branches, they can be removed. You can find an arborist by visiting this web site and clicking on Find An Arborist. You can put in your zip code:  http://www.treesaregood.org/