You absolutely can teach an old dog new tricks. Your first step is to make sure you are bonded and then he/she will do anything to please you. Although dogs (just like people) learn more quickly when they are younger - the learning never ends. Patience, consistency, and positive reinforcement are the keys. I rescued a Lab 10 years ago (at 4 years old) and he had never been trained. After a couple of years he knew all kinds of commands.

Good Luck to you!!!