Breastfeeding tips- milk takes 3-5 days to come in for most women, up to a week for others. Don't worry! Up to an 11% weight loss is normal and ok in a breastfed baby (less for bottle fed).
Thrashing, pulling away, screaming at your boobs as though you are trying to poison your baby are all normal behaviour and a way your baby stimulates your milk supply. It is not an indication of insufficient milk or baby not being satisfied.
Check for wet and dirty nappies, they are the only indicator of sufficient supply that you need- weight gain is another indicator but only after week 1.
Topping up with formula may be required, but the more you top up, the less milk you'll make, so the more you'll need to top up. Eventually your supply will dwindle.
If in doubt shove a boob in the mouth. (Some) Breastfed babies feed very frequently, they also like a boob for comfort. Don't worry about routine or a set feeding pattern, they'll feed when they want. Again, it isn't a sign of low supply- boob, unlike bottles has many uses for a baby beyond food. Bottle fed babies obviously get those needs met in other ways.
Learn feeding cues- opening the mouth, turning towards the person holding them, sticking their tongue out. Feed them BEFORE they cry, makes latching easier.
Cluster feeding- look it up, understand it, prepare for it!