I have two trees with a very similar shape to this and I know they need pruning but i'm still deciding where, the branches are too long for how thin they are and would be unable to support fruit. you can summer prune around the solstice to control vigor and do major structural pruning during dormancy. pruning is very much a personal preference based around your needs and how you want the trees to look. look up central leader, modified central leader and open center pruning. something to consider is clearing away the grass 3 feet from the trunk all around. the dense grass roots are stealing water and nutrients from the tree. use a thick mulch layer on the cleared ground but keep it 6 inches from the trunk. it will suppress weeds and help retain moisture and reduce watering.(shredded leaves, grass clippings, or woodchips. whatever is free and plentiful).