I use the power supply from Digitec (https://www.galaxus.ch/de/s1/product/digitec-gan-4-port-fast-charger-130-w-usb-ladegeraet-24556945) and it works perfectly. However, I have noticed that not all USB-C cables allow the same charging speed. But the cable supplied works great.

You simply need a USB charger and a USB-C plug, for example the Ugreen Nexode Bundle with 140 watts (available here at Galaxus). Fits together perfectly and also charges relatively quickly.

So you can charge the power bank via USB-C. You will need a USB-C cable and power adapter for this.

You should have a powerful charger. Then simply connect it to the bottom left USB socket.