Your tree is obviously under stress. Here are a couple of observations that may be helpful. First, it appears as through there is a mound of dirt/rocks in front of the tree. Because the majority of tree roots are near the surface, they are easily damaged or killed when additional soil or material is added to their root zone. It cuts off their water and air supply and they need both. The largest limb damage/loss is in the area where the soil level has been significantly altered. The remaining root system under the tree is covered with rock so we’re assuming it’s not in irrigation? The tree may not be getting enough water. Once a tree is stressed, it can easily succumb to other diseases and pests. You might consider asking your local nursery for a recommendation to a reputable arborist who can come and determine the extent of damage, if the tree can be saved, and if it can, what measures need to be taken to bring it back to health. An arborist can also prune out the dead and dying branches and make recommendations for watering, fertilizing, mulching and soil grade changes.