According to the product description, an output of 20V and 2.25A is possible, so it should work. I don't have any experience with the Samsung notebook, but my Thinkpad is charged with the specified 45W via PD without any problems.
There is no information about resistance to water/moisture in the technical characteristics. There is an LED display and a button on the top. There is no protection against water at all. Nor is there any on the front side, where the various USB ports are located.
Must have been taken over incorrectly :D here is the original text: https://www.xtorm.eu/de/product/xtorm-45w-usb-c-power-bank-infinity-27-000/ "With this large amount of energy, you can easily charge a smartphone thirteen times or a tablet or MacBook at least 1.5 times."
The technical data sheet [1] is linked in the item description. It states:
Output:
3x USB 5V/2.4A, 3A max.
1x USB-C PD 45W (5V-15V/3A, 20V/2.25A)
Total output 60W max
Input:
USB-C PD 5-20V/3A
Yes, this power bank supports USB-C PD (input and output).
[1] https://static.digitecgalaxus.ch/Files/1/0/0/4/1/3/2/9/XB203%20-%20Xtorm%20Power%20Bank%20Infinity%2027000%20Leaflet%20DE.pdf