Breastmilk in a bottle question!!!

So I have started to feed my one month old baby a bottle I have a few questions

How much do I feed my baby each bottle ?

If he doesn’t finish the whole bottle can I just put it in the fridge and give him the rest when he he’s hungry again?

How do you put the breast milk in the bottle from the storage bag ? Just pour it in ? Do you cut the corner and then pour it from there ?

I just need any tips with it if anyone has any?

I want to do everything right!!!