my baby girl was crying a lot 20 days old can I give formula milk how can I know breast milk is sufficient for my baby

A. Yes if your child is not sufficiently gaining well or is full with the fee that you give then of course you can give formula to the child it is not a problem other than that I also if your child is full for 2-3 hours after taking a feeding gaining about minimum 500 g in a month it itself is a sign that you’re feeding is enough otherwise it may not be enough for the child