Is it okay to reproduce the work as a teaching assistant? Next week, I need to give a lecture on a topic (say T).
I surveyed over the internet and found excellent video lectures by a professor (Say P).
I learned T thoroughly. I can able to answer any question. I can able to clarify any doubt.
But I may undergo the following problem:

I may end up in reproducing the same content in all aspects (lecturing
flow, motivations, examples, notations,...). If any of my students watch the lecture
series of P after my lecture, they can easily realize that I reproduced the
same.

Is it a problem or is it normal?
I am feeling it as a problem because of the reason that I feel that my lecture is a subset of the lecture by P. And there is no contribution of mine other than reproducing.
I agree with user11388 that it would be good to &quot;cite&quot; the video you used, but otherwise I wouldn't worry much about this. Truth be told that most of us in academia, in the early part of our teaching career, &quot;emulated&quot; the teaching of our own teachers, especially the ones we most admired. Over time you learn to be more spontaneous, but at the start you try to follow a good model. It is partly what mentoring is about.
However, you will &quot;add value&quot; to the lecture just by being there to answer questions that might arise and to (hopefully) watch the student's reactions so that you can notice difficulties of comprehension.