I share your pain and although I don't have a solution (almost in 2020...) I do have a viable explanation why they keep it this way.
Two factors, based on my thinking:
- They don't want to show an empty card, so they switch to another source when a dictionary definition is not found. (to Wikipedia)
- They have to pay for translations over a certain quota, ...
It depends if the books have DRM (Digital Rights Management) or not.
If they do then you can only read them on Amazon devices or with a Kindle app on PCs Macs Android or ios.
If not DRM then download them to a computer using the transfer by USB option on the "manage your contents and devices" page on Amazon on the Web.
Then you need to convert your ...
Games (and Apps) for Amazon Kindle Paperwhite are known as an Active Content and you can search Amazon Store for them here. Some of these games are for money, some are free.
However as stated here they are fully supported on Paperwhite 1 & 2 and partly version 3, version 4 is not discussed at all. You have to test each and one you wish to try. Please ...