I think the easiest way to create a multilingual form is to use repeated table join
E.g news articles.
table1 is for news id, perhaps some date(time) field etc
table2 has id, some parent_id pointing to table1.id, title, description, etc etc and language field.
You create a list on table1
then create a join in table1 list admin - from table1 to table2, from id to parent_id
and make the join repeatable.
Perhaps you want to create a dropdown element on language field.
OK, when all is done, you can try to enter news articles. You open the newly created form, write title, text and choose language. e.g English
Then you click the button that opens new group with title, description and language fields. You write the same news article for example in French and choose then 'French' in language field.
Then you can create third, ..., n-th language version of news article.
The list data can be filtered by language.