Q.Guava Tree Dying
I have a Guava tree in Pakistan, which is almost 3 years old. I planted it as a grown tree from the nursery. It has been giving fruit regularly. And few months back it started giving more fruit than expected. But suddenly all the leaves has started falling and the fruit has stopped growing too. What shall I do? Any opinion will be much appreciated. Many Thanks.

Inspect the leaves and tree for any signs of pests or disease.
These links will help you determine the cause.
https://www.gardeningknowhow.com/edible/fruits/guava/growing-guava-fruit-trees.htm