"There are a lot of people and few desks here."
Translation:Тут много людей и мало столов.
would "а" fit better than "и" here because you are comparing a large number to a small number?
That would sound unnatural. If you want to emphasize that there is not enough tables for all the people, you'd say "Тут много людей, но мало столов". But then, you'd also use "but" in the English sentence.