If an entity doesn't see a good way to invest money, they won't borrow money to make money. This is what they mean when 'the demand for money is low'. If the government borrowed money, they would not make as much on that money as the interest payment to who they borrowed from, so they never borrow the money.

This has the overall effect of reducing money demand, reducing the premium to get that money (the interest rates continue to drop). Everyone though 0% interest was a hard line and you couldn't go lower, until negative interest rates were introduced to try and reverse this trend, which it largely hasn't.

What part of it? You are a bank and try to earn as much as possible with the money your customers gave you. However, states, consumers, and businesses don't invest as much as they used to / don't borrow as much money. What do you do as a bank? You lower your interest rates to try to attract at least some customers. Combine that with exceptional supply due to quantitative easing and you have what you have right now

Lower interest rates cause people to wait for a lower rate, higher rates cause people to take out loans before the rate goes up again. CBs did the worst possible thing with no historic evidence it would work, as usual.

Why is that so complicated? If the demand is low but the supply is high, prices usually decrease.

"Money" is cash now. Price is the interest.