I have several redwood trees in my yard. The lower limbs have gotten too long and impede my deck. If I cut them back will they die or will they green on the ends?

I’d also like to climb the trees and then thin near the top so I can get light on my pool again. If I cut the limbs back at the top could that kill the top? I know not to top the tree but I’m wondering if I thin the limbs if the tree could die or grow too much more.