u/BacktoBuxtehude51

I'd like to try to save it but i'm not sure what the sickness is.

Google Lense says "The item pictured is a mango tree leaf displaying symptoms likely caused by mango bacterial black spot, a disease caused by Xanthomonas citri pv. mangiferaeindicae. "

The tree's fruit is sickly, does not grow to size and they all seem to turn black and fall off prematurely.