Was Friedman wrong about inflation? What causes inflation?

So I guess my core question is what causes inflation. However I previously thought knew that one of the main reasons for long term inflation was an increase in money supply. However recently I saw a video of a German politician saying that this is wrong. In essence, someone said that when the government prints more money inflation rises. She responded that that’s the wrong money theory. That friedmans theory has been disproven.

Upon googling I also found this article:

As economists are today, Milton Friedman was wrong about inflation

The point is essentially (if I understood correctly) that printing money does not cause inflation because just printing money doesn’t create anything and therefore the market doesn’t accept that money.

The article sums it up by saying: „inflation is not a function of increases in so-called “money supply” as Friedman contended. More realistically, it’s the money that’s trusted the most that is circulated most widely and in the greatest amounts.“

I’m aware that there is supply side and demand side economics but I didn’t know the differences were this large. Most of my life I was very confident in the principal answer of what causes inflation (especially because it’s taught in schools like this)