Young Plum tree

Question

Leaves are crinkled and almost no fruit.

Answer 1

This is one possible answer: https://www.gardeningknowhow.com/edible/fruits/plum/control-leaf-curl-plum-aphids.htm
Your local Master Gardener could probably identify your problem exactly. Here is a link that will put you in touch: http://mastergardeners.org.uk/get-involved/find-your-nearest-master-gardener/