Hello. Please help me to formulate the assignment correctly:

"Speak on the question from the theoretical course in Indo-European Lexicology: The native word-stock of Indo-European languages",
The course is Indo-European Lexicology,
the native word-stock... is one of the questions of this course.
Maybe, "a theoretical course in ...". Do you think it's possible to say "speak on the theme"?
I will be very grateful for your help.
Thank you very much.

If you expect students to actually speak, then use "speak." But if you want them to write, then say "Plan and write an essay ... "

Certainly! Based on your description, here is a revised formulation for your assignment:

- "Give a presentation on the topic of 'The Native Word-Stock of Indo-European Languages' in the theoretical course of Indo-European Lexicology."

By using the term "topic" instead of "question," it gives a clearer indication that you are expected to speak on this specific aspect of the course. Additionally, using the term "theoretical course" clarifies the nature of the course you are referring to.

Regarding your question about saying "speak on the theme," it is indeed possible to use that phrase. However, using the term "topic" is more commonly used in academic settings and may be clearer in this context.

I hope this helps! If you have any further questions or need additional assistance, feel free to ask.