1. A lake is usually freshwater, whereas lagoons are bodies of salt water separated from the sea. Lagoons can also be bodies of freshwater bordering flowing waters or rivers. The main difference is that a lake is typically alone standing, whereas lagoons are separated from other bodies of (running) water. 2. "What can I do for you?" is correct. You put the person you're addressing after the preposition, in this case "for," but also in cases like "I will send this to you" or "She threw the ball at him." 3. It is literally a house on stilts. If you search it up online, images of houses on raised platforms (usually) made up of wooden bars. They're very normal to see in areas of the world where floods and high tides can affect villages and inhabited establishments. I hope this helped! Cheers :)