As far as I understand, bitcoin doesn't eliminate the ability to use debt.

What I don't understand is why bitcoin is inherently deflationary. Wouldn't it depends on the economy / GDP? If the economy is growing, bitcoin acts in a deflationary manner, but if the economy shrinks, bitcoin will be inflationary. Right?

Is there an assumption that the economy will always grow, or always be desired to grow? More of a philosophical question, but is a continuously growing economy feasible (or desirable) in the long run on a planet with finite resources?