If the translated file did not work, probably there is a bug on it, we'll take a deeper look into this. But for now, let's translate the upsell heading manually via a template. To do this navigate to: \x\woocommerce\single-product and copy the file up-sells.php
Then navigate to \x-child\woocommerce\single-product (create this path if it's not existent) then paste the up-sells.php file there, open/edit it and you'll see the You may also like… phrase, translate that to the proper phrase then save.
Make sure to clear your browser's cache and all your caching plugins/feature before previewing the page.
Hope that helps,