I tried doing this with Japanese. It was.... not a success.

For one, the Japanese version isn't translated greatly, and while there are some mods that rewrite some stuff to sound more native it's far from perfect as they can't change spoken dialogue that much.

Then, many words are just the English ones in katakana. Now technically that's fine. But when the whole game is full of words like "furosuto baito supaidaa" (written in katakana ofc) it just doesn't sound too well, nor does it teach you a lot of new words per se. I guess it at least gives you a feeling how katakana is used to write foreign (loan)words.

But then, I walked into the in Whiterun and heard the bard sing Ragnar the Red in Japanese. The lyrics to some sentences are twice as long in Japanese, smashed into the same melody, causing it to sound like a synthesizer going over the sounds quicker than humans ever would.

I just gave up. I can play the game for the most part without understanding anything, so I thought it would be a good practice as not understanding something wouldn't get me stuck per se. But in the end, it wasn't very handy.