You're not wrong about interest banks, but in regards to inflation you actually have it backwards. Inflation is the expansion of currency, not the rise of prices. Definitions get entangled because inflation causes a rise in prices, and people don't know better. Expanding the currency increases the market availability of said currency, thus making it less valuable relative to other goods.

Think about the word inflation. If you inflate something, are you raising it, or making it bigger? Inflating a balloon with helium is not the act of raising the balloon, but rather expanding the balloon. That expansion triggers a rise when it's helium. Likewise, inflating the currency is to expand the amount of currency.

Inflating the currency too much causes there to be too much money chasing not enough goods, as you describe