I don't have a Kobo, but found it difficult to navigate the Kobo site for foreign books, especially because Kobo
refuses to let me go to the German or French store - it always redirects me to the US store. I hate it when websites do that.
What I personally do is browse amazon.de, amazon.fr and amazon.es for book suggestions, then enter the title in the US site (my Kindle account is registered in the US, so it's the only Amazon store that I can purchase books from). Some books are not available here, but most/ very many German ones are. Also, when you click on an author's name on amazon, it shows you all their books, including all the translations that you can buy.
I work on Windows, so things may be much easier for me, and I run the books through Calibre anyway (it takes only the press of a button), so the format does not really matter to me. Amazon is the only store that at least does not hinder me from buying the foreign language books I want.
If you read a lot, I would also suggest getting a US libarary card -
there are a few that let non-residents do it for a small yearly fee. That would cover the English books.