I wouldn’t put so much pressure on remaining consistent. I actually think it’s kinda nice to have a mix of languages represented on your bookshelf. Generally, I prefer reading a book in its original language if I’m able to because things can get lost in translation (literally) and it improves your skills in that language. However, you do need more than just a little knowledge of that language for it to be enjoyable and some books are difficult to read even for native speakers, so it might make sense to grab a translation for those books or for people who are only just starting to learn a new language. There’s not shame in sticking to translations, even if you could technically read the original!