I wanted a card reader that didn't cost too much but did use USB3 because of the transfer speed. After not too long searching on the coolblue website, my choice finally fell on this one.
The next day I was able to use it immediately, and this went without a hitch. I plugged it into my PC, didn't even need a driver, it literally worked straight away. Perfect.
After working for a while I had to transfer data from an SD to a MicroSD card, so I put both cards in, put the stick in my PC, and... nothing. The cards were seen by my PC, but couldn't see any info about them (no saved data, not how big the storage capacity was, etc). With every interaction with the cards I could wait endlessly and nothing happened.
It has been concluded from this that the device probably does not take into account the connection of several cards at the same time and that they probably send conflicting data to the PC, so that it cannot process the data properly.
In short (TL;DR):
Great small and compact device that does what it's supposed to do, but only with 1 card at a time.