At the beginning of the game, you have five lives. You will lose a life for each level that you can't complete. Be at ease, though! You get a free life in Mayor Match every 30 minutes, so you can quickly go back to having 5 lives left.
Five extra lives are yours to keep and can be requested from your teammates at any time.
Your request will be sent to your team when you tap the "Ask Lives" option in the Team menu, and any teammate can respond by sending you a free life! It costs nothing to send lives to your teammates; in fact, by helping one another out, you earn free coins.
With your coins, you can also get a life offer!