This is it, thanks!
I'm sure that the functionality will be useful for part of Czech readers. You can always turn it off.
Polish translation is already finished. However, there are probably a lot of mistakes.
It will be easier for me to correct mistakes (especially too long strings) when I'll see them on my device.
I please you to prepare the installation package, when you can find same free time.
PS. Kindle User Guide is not translated to Polish and you can remove it from installation process.