No need to learn it, I've already done this years ago. And this is not the way to fix an issue like this.

Within the Witcher series I liked both german and english voices but I do prefer my native language which is german. I guess that counts for a lot of other german players, too.

Besides this, german voiceovers have a long history. Since the beginning of movie making in Hollywood there were made translations of it. And you know, after decades of doing it this part of the industry gained perfection as well as high reputation. Not only because this work is done by known and experienced german actors and speakers but also because the german language can make use out of much bigger vocabulary than the english language to express nuances and feelings very individually (from this point of view it must be great to understand japanese or chinese...).

You are from Serbia and I personally think serbian is a very nice language to listen to. Unfortunately I do not speak or understand it but I would prefer it in a movie or a video game if I would be a native speaker. It just has to be done the right way. Unfortunately in many countries it seems easier to listen to the original sound and just add subtitles to it. This basically works (and is also good to learn a different language) but feelings and emotions cannot be expressed correctly.

Back to topic: What went wrong in Blood & Wine is probably not the recording but the mixing of the voices. The main speaker of Geralt is the same but the effects that have been added to the voices after recording are different from the original W3 or Hearts of Stone. In my opinion this is reversible but includes some effort to do so (every sound file would need to be re-arranged and implemented into the game through an update). In some way I do understand CDPR in this point but what I do not understand is the poor quality of testing this before the release. They have a final product now and they currently do not want to spend money for a minor flaw (minor in the eyes of CDPR). This is something we can blame CDPR for. What we hope for is that this failure does not happen again in a future title...