Hello guys, I have around 45000 AA miles, what would be the best way to redeem them. I checked it isn't even enough for me to travel for one person, any suggestions?

Just depends where you want to travel. You can check the AA award chart. Domestic travel requires 25k miles for round trip, Mexico and carribean requires 35k (I think). Also, 40k will buy you one way ticket almost anywhere from US. So, you actually have options and just figure out what you want to do it. If you like to travel, use it for yourself. You will get most bang of the the bucks. If not, you can just sell the miles to the brokers and get some cash. In addition, you could upgrade your seats when u fly AA partner airlines like Etihad, Qatar and Cathay Pacific

Can you sell American airlines miles? I didn't knew that, do you know any reliable sites / broker?

You need to book in advance. AA has very limited super saver availability these days. For now bank it until needed.