You can always borrow from the bank or the loan shark, or even both of them. Occasionally all it takes is a little extra money to make it. If you are in real trouble, sell back the upgrades that are not necessary for making it to the next round.
-You have to go bankrupt in order to have the option to retry a level. Do this by getting a negative cash balance. First, go to the Upgrade screen and sell all bought upgrades. Sell all your movies, then go to the "Loan" screen. Raise your daily repay amount to a value greater than what you have. Click "Accept" and you should go bankrupt. You can now replay the level.
-To become bankrupt, first borrow $5,000 from the loan shark. Have no movie playing and start the day. Keep doing this. Eventually a message will appear, stating that the loan shark demands his loan back. If you have $5,000 or more, do not start the day. Instead, look for a movie that costs enough for you to drop below $5,000 and buy it. You can now start the day. At the end of the day, a message will appear, stating "We steal your credit". They should take $5,000 and you will then have negative money. Start the day to restart.