Aphids and compost

Hi all

This is my second year of vege gardening and was hoping for some advise re aphids - they were on everything last year!

I have also recently started composting and my compost bin is full of little flies - mainly tiny whiteish moths ??white fly - is this normal? Do I need to try and get rid?

Also could I please pick brains re mildew - had issues with this on my peas and courgettes/pumpkins last year.

Thanks in advance.