The second link that coplate posted above:
https://tribut.de/blog/amazon-kindle-and-eduroam/
looks like you best choice.
You will find in the directions that you have to convert the certificate format.
If you don't have a means to do that on your PC, your Kindle has the software pre-installed that will do that, but the Kindle has to be jail broken to run the command.
The Kindle also has the various utilities pre-installed to trouble shoot the problem.
But again, you have to be jail broken.
Since you have already installed 5.8.10 you can not jb the one you have.
Send yours back under the "no questions asked" return policy and then either purchase a refurbished one or a new one from Amazon (Germany).
Do not allow this second one to connect with the Internet until after you have jail broken it.
Once that is done, then you will have a means to run command line commands on the Kindle and we can walk you through updating the information from that blog about getting a PW-1 to work.
I.E:
You get the feature you want, we (and the world who can find us) get an updated setup procedure.
If you have trouble with following the current jail break instructions, just post here, we can probably find someone that can walk you through them in your native language.
= = = =
PS:
I think we will find that the password referred to in the setup panel is for a password protected certificate.
Since the certificate already authenticates you to the network.