ERR_TOO_MANY_REDIRECT when using slugs for blog pages in multilingual website

Hi all,
I’m trying to setup a multilingual website (english and bulgarian) that has a blog. I want the link of every blog post to appear in it’s own language. So first I tried to add different slug for every one of the post languages - for example - Test for en and Тест for bg (this one in cyrilic). This method worked only partially - when you click on the title of the blog post, it opens the correct link, but when you switch the language, it starts to use the folder structure instead of the slugs. Then I found somewhere in the forum, that I need to enable pages: Redirect default route. So I enabled it, and then another problem appeared. As long as the bulgarian slug is in latin it works, but when I write it cyrilic, it gives ERR_TOO_MANY_REDIRECT when I try to open the post.
Can you tell me what I’m missing here?

And one additional question: how should I construct the page slugs in order to make the links shorter and not showing the whole folder structure?