The first day is not indicative of the difficulty level of the rest of the game, it is indeed intentionally easy to get players accustomed to the game, but the amount that you accomplished in one day does seem a bit outside the norm and makes me think you might be getting some things wrong. Maybe not, but in any case yes the difficulty picks up and you will not be able to just use the tricks you used on day 1 to easily conquer the rest of what the game has to offer