My mango tree is 5 years old. and is 1.5m (5 feet). It flowered last year, and fuited but the fruit only became pee sized before falling off. It is starting to flower again, but this time i want fruit that you can eat. ALSO, it has not been grafted. Is it really necessary?

Grafting will produce more edible fruits faster. If you want to have edible fruits the natural way, you fertilize it, but it will take longer.