I’m not sure if this will help with your translation, but I was able to change the text of the “Browse Wishlist” button by hooking into a filter. (This would go in your functions.php file)
function edit_browse_wishlist_label() {
return 'ENTER YOUR LABEL HERE';
}
add_filter( 'yith-wcwl-browse-wishlist-label', 'edit_browse_wishlist_label' );
To change the “Add to Wishlist” text, you can do that within the settings page. (Woocommerce Settings -> Wishlist -> “Add to Wishlist” Text) Otherwise you can edit the filter in the same manner as above, using yith_wcwl_button_label
when you are adding the new filter.
If you still want to just edit the php file, it is located within the file class.yith-wcwl-ui.php
.