Are there any issues with submitting conference papers in one language and publishing them in a journal in a different language?
As stated in the comments. It is totally irrelevant if they are in two languages. If it would be ethical to do this one language then it will be ethical in two. If it is unethical in one language then it will be unethical in two. In my field presenting at a conference and then submitting a paper to a journal is just fine, as long as the conference does not publish a proceedings or similar. In other fields, it is not acceptable. Again, the language matters not.