Help please and solution welcome.

Serious Infestation in my little garden.
1. Lime butterflies caterpillars (Papilio demoleus) are messing up the young growing citrus plants in my garden eating up the citrus leaves and the tender leaves are curling. The tiny snails could be seen in the pix

2. The bitter-leaves plants are being attacked by tiny white-flies.

3. The garden or soil has this small snails that doesn't grow more than the size of a bitter kola or dart fruit. eating up my my vegetation they hibernates during dry season and appears during raining season.

4. The mango tries are been covered by the regularly thick flies we all have around , not sure what is breading them. Cos my neighbour has a small fish pond. Google d it---- says it is Mango gall flies (Erosomyia mangifera)

please any solution would be appreciated.


Thanks

Sharpshooter insecticide small bottle that goes for 1.5k shud settle your troubles