So now you’ve done both halves of the equation, money coming in and money going back out, so you can put those two halves together to calculate the cash flow, and the cash balance.
Cash flow is the change in the cash balance from month to month. You get that by adding money received and subtracting money spent.
Cash balance is the amount of money on hand. You get that by taking the previous month’s cash balance and adding this month’s cash flow to it — which means subtracting if the cash flow is negative.
Having a negative cash flow every so often, for a month, isn’t a big problem. You should never have a negative cash balance. That’s the same as bouncing checks.