How much is "a quarter of a lesson" - some lessons last all day, others less than 30 minutes in my experience.
However a few thoughts on 1)
Depending on how you made your ester, it could either be an equibilbrium between alcohol and acid, and ester and water.
In one form, Le Chatelier's Principle states that if you remove products from an equilibrium the equibilibrum is shifted towards products.
Another way to make esters is alcohol and acid chloride to ester. This way is less reversible, but the acid chloride reacts with water to give back the acid, which could give you issues as per the first point.
As to part 2. Are alcohols, acids soluble in water? What about esters? What is the "mechanism" for being able to smell things?