Do not stop doing good deeds even after Ramadan. Don't be just a 'Ramadani' Muslim, instead become a Rabbani! Check out how you can continue the good work even after the holy month of Ramadan.
One's entire life is not enough to count the innumerable blessings of the Almighty Allah. So, utilize the time remaining in your life usefully. And adhere to the right path, Siratul Mustaqeem without fail!
If you have missed any fasts, first finish them without fail. Obviously, you would have missed the fast/s for genuine reason/s. Because if a Muslim misses even a single fast without a valid reason, his/her entire lifetime of fasting will not suffice for that single missed fast!