What two things does Twain discover during the first two weeks?

The answer is in chapter 6 of the book. The narrator has always longed for a trip down the Mississippi and finally this dream comes true when he gets on the steamboat Paul Jones. He decides to sail all the way to the Amazon for an expedition. After spending two weeks making the voyage from Cincinnati to New Orleans, however, he discovers two things. One is that it's going to take ten years or more for a vessel to reach the mouth of the Amazon. The other is that he does not have enough money to carry out the exploration as he has planned, even if he takes a ship. Therefore, he sails back upriver and takes this opportunity to learn to become a pilot with Mr. Bixby.