Breast feeding

Hi all readers. Want to ask for your opinions. Currently I am pregnant with my 2nd child. And at the same time my first child want to start back with breast feeding. But my milk supply is not enough and stop due to not enough supply as I've tried so many tips as given by family, relatives and friends but the supply is still low. Here's a few question. 1. Is it possible to breastfeed my 1st baby while I'm pregnant? 2. Will it affect my 2nd baby? 3. How to restart back with the supply? 4. Any tips and tricks on how to increase the supply? Truly appreciate your help. Thank you