Hi there,
what is the idea of storing the solenoid valve and the vacuum pump?
To have it in the outdoor box? How should the tubes run out of it? How should the vacuum pump suck air
into the tube when the box is “hermetically” sealed to be water proof?
The solenoid valve is currently stored inline with its tube and the garden hose. Mine is just resting in the grass, though you might want to mount it to your raised bed to get it out of the way or cover it with a small plastic container. You could maybe even burry it?
The sockit box is not hermetically sealed or waterproof - it is rainproof which will allow it to protect what’s inside from the rain, but it can’t be submerged under water 
So storing the vacuum pump inside works because air can still get in/out, especially where the cables and tubes enter and exit the box. If you want, you can add an extra bit of tubing from the vacuum inlet to the outside of the box, or just from the inside of the box to the outside to facilitate air flow.
The pump actually sucks air in from the tool and pumps it out into the box, so it’s actually forcing air to blow out of the box instead of sucking it in. If the seal isn’t tight, it should work just fine, even helping blow out any moisture that might be in there.
Ah yes. I got my all my airflows backwards! 
Just edited my post.
I connected both devices with the pinning as seen in the CAD drawing in the documentation. Both devices work
like this.
As there is not labelling on both devices (vacuum pump and solenoid valve) is this of any matter or could I plug
it in vice versa?
Yes, the polarity of the vacuum pump and solenoid valve wires do not matter.