ETF price: how is it settled?

I think I get it how prices of individual stocks are set during a trading session: there's bid and there's ask, people sell to other people willing to pay the asked price. That's pretty straightforward. Now, an ETF is a bundle of stocks. Nobody own “pieces” of an ETF, its prices is dictated by the prices of the stocks in its composition, right? Nobody is buying or selling VOO, there isn't a supply of VOO stocks somewhere, people are buying and selling Apple and Microsoft individual shares and that dynamic dictates the price movement of an ETF. Am I getting this right?

Now, what about VUAA.DE, an ETF traded in Germany that follows S&P 500? When the German stock market opens, the US stock market is closed. What moves the price of VUAA.DE then, since no one is trading Apple and Microsoft shares at 09:00 UTC.