Q.orange tree
My orange tree is housed in the greenhouse over the winter and usually likes the conditions; however, this year the leaves have dried up to a crisp on 2/3 of the tree but have remained on the tree. NOW there are a lot of shoots coming from the base of the tree probably 2″ from ground. These look healthy but spoil the look of the tree. I have had this tree 3 yrs and it is grown in a tub. It is a navel orange. Can you advise me please?

It sounds like your tree may have experienced some winter loss and the shoots growing from the base of the tree are likely growing up from the root graft.
Remove the suckers as indicated in the link below.
You can also trim away the dead and damaged portions of the tree.
Also a link to refresh you with care of the potted orange tree.
https://www.gardeningknowhow.com/edible/fruits/oranges/orange-tree-container-care.htm