Hi! As a player, there are a few things I can answer:
"I'm getting a bunch of secrets that give me like 1k% more "money" but it doesn't do anything."
"I buy 1 intern and it tells me that it's producing 33/s but i earn 31k/s instead."
-> Anything that gives you xK% more money is summed under "Profit", when you click on the amount of money you have, at the top of the game.
Owned: X amount of money
Bought: X amount bought with stock
Profit: xK%
Base Gain : x/s -> an amount that takes into account the profit multiplier.
"HR doesn't do anything"
-> HR is the most efficient building for me so far, as it produces people and not money.
Your money production gain is therefore multiplied by the amount of people produced... etc
"Contracts 1-3 were very easy and didn't take long at all to get, but contract 4 is an extreme bump in difficulty."
-> I agree, there is a definitite bump in difficulty at that point, and both rewards are worth it. That is, +15% for interns, and unlocking #005 Contract
Progress on the contracts becomes steady again until #015 Contract, where you reach a new bump.
I feel these bumps are there to make us think of a more efficient build, so it really works for me.
Also, keep in mind there are a bunch of bonuses that are doing nothing until you unlock what they boost.
Hope it helps!
--
Dewin