Here is a learning support on gerunds and pronouns. This is about a half-page of text, so there is room (and the latitude, since, like just about everything on this blog, this is a Microsoft Word document you can manipulate for your particular use) to make a worksheet of this should you see fit.
Basically, the text here explains the proper use of possessive pronouns following gerunds. It’s both simple and complicated at once, but as Paul Brians explains (this is drawn from his book Common Errors in English Usage), the advice in the passage will improve the quality of student writing.
If you find typos in this document, I would appreciate a notification. And, as always, if you find this material useful in your practice, I would be grateful to hear what you think of it. I seek your peer review.