Q.Cherry tree…no fruit and leaves
The leaves have a black substance like eggs and a lot of ants on the tree.
The black substance is sooty mold which is a type of mold that grows in the honeydew secreted by aphids. Wherever you have aphids you typically have ants because ants and aphids have a mutually beneficial relationship. Ants protect aphids in return for honeydew.
Here are some articles on sooty mold and aphids that will provide you with more information, including a course of treatment: