You can get Thrill Points for doing almost anything, such as riding a coaster, running a mile, painting a stall, etc. You will advance to the next managerial level if you get enough thrill points. A good way to earn Thrill Points is by picking up shiny signs that can be from shrapnel to an anti-Thrillville ad.
When fighting a new enemy, the HP does not change much. The first Boss is similar to two minor enemies you encounter. Be careful of the "frog" enemies.