Moodle Webservice API dont returns correctly

Hi there,

I am currently trying two methods of web service API (Moodle 2.6) to call with REST:

#1 core_course_get_categories
#2 core_course_create_courses

With both I have the following problems:

#1
The function returns me categories back but unfortunately no subcategories. Even if I add like the documentation says the parameter "addsubcategories = 1", only the top-level Categories are sent back. An idea what the issue could be?

# 2
The course creation works so far, but I would like to assign the instructor to a specific user. Now when I create a course, it is indeed created under the users with the WS-rights. Is there a possibility to change the instructor?

Short background:

We have a central system where teachers can save new course information. Here should you have the opportunity to create a Moodle course immediately. We have in both systems a unique identifier of the user that should become the instructor. Of course, must be prior to the course, the Category / Subcategory be selected.

I would be happy about feedback!