Signed up for a talk, not enough material I am a PhD student in pure mathematics about 4 months into my program. After consulting with my supervisor and some peers, I have signed up to give a 20 minute talk at an online conference, which has invited final year undergraduates writing a bachelor's thesis, masters students, PhD students and postdocs to sign up and optionally give a talk.
My supervisor and peers have told me that it is a good idea to sign up as it's really good for my CV. At this point in my program however, I am mainly learning about my field, and haven't produced very much original research. I have however come up an (in my opinion) interesting question that would make for a good talk if I had a partial answer, but at this stage I have not had much time to explore the answer.
The conference is in about a month's time, and I think it would be a great exercise to write a talk giving an introduction to the field and how it came about, but at this stage this is all I could do, and even this would be quite a task to do in a month!
The sign up page for the conference does encourage works in progress however, but I am not sure how much I can do in a month.
My questions are:

Was it a mistake to sign up for this talk?

If, in a week's time say, I feel that I can't present any partial progress, can I ask to be removed from the schedule, or is this unacceptable?
Twenty minutes is not long for a talk.  Moreover, most students drastically overestimate how much material you can put in a short talk.  Giving a short introduction to the field and how it came about will be more than adequate to fill that amount of time, and would be a perfectly reasonable topic for an incoming PhD student with only four months in the program.  Time permitting, it might also be nice to mention your research question and the general avenues of inquiry you are going to use to solve it.  You should also leave a few minutes for questions and comments, particularly since this will give researchers in the audience an opportunity to offer suggestions on your research idea.
So no --- you didn't make a mistake signing up for this talk.  Don't bother trying to cram out new research results for it --- just stick with your plan to give a short introduction to your field and a brief outline of your research question.  That should be enough to hold people's interest and solicit some questions, and the twenty minutes will go by in a flash.  I doubt a short talk like this is really going to help your CV all that much, but it will be good practice for giving conference talks, and if you are lucky, it might precipitate a longer conversation on your research idea with one or more of the researchers in the audience.
(And as Buffy points out in the comments below, no one will be upset with you if you don't use all your time --- running over time is bad, but having time to spare is fine.)