Q.Yellow leaves on my small orange tree
What can I do to help my orange tree with yellow leaves. I have had it for nearly 2 years has never had fruit & doesn’t see to have grown very much.

Your lemon tree could be getting too much water or could have a disease that's causing the leaves to yellow. These articles may help you:
https://www.gardeningknowhow.com/edible/fruits/lemons/lemon-tree-not-fruiting.htm
and
https://www.gardeningknowhow.com/edible/fruits/citrus/tip-on-water-requirements-for-citrus-trees.htm
and
https://www.gardeningknowhow.com/edible/fruits/lemons/lemon-tree-leaf-drop.htm