Help with bank account formula

Hi, to start, i am not an expert, i know the basic of the basic, i've been building my spreadsheet by searching the internet, but i came to a dead stop, and i don't know how to search this on google.

What i am trying to do is a spreadsheet that can keep up with my finances, the amount of money in my bank account, my income, my outcome and a money goal.

i had to try an if function to hide the value if no data was showed, and that messed up all other functions that i had. I had a simple add the previous bank balance + the remaining value from (income - bills), but the if function made it so i can't use the previous value if no value is imputed.
so now i am trying to find a solution for showing the current bank balance based on income and outcome, but i need it to be sequential.

I attached a picture with what it used to be and what it is now, i hope it helps you understand what i need.

Untitled.jpg

basically what i need now, is on the line bank and goal, on every month, it will update the value based on the previous one, but since the function if won't let it do that, i don't know what else to try.

Thank you.
PFC Carlson, Christian
US Army