Check this out under Conference pedagogy and planning: https://cassidyinview.wordpress.com/by-topic/conference-pedagogy-and-planning/feedback-forms/simple-feedback-form-2/
It’s a template you can download and adapt for your own use. There are other downloadable feedback forms at Conference pedagogy/Feedback forms.
Watch here for more conference and workshop/seminar related ideas. This feedback form will appear in an upcoming book about Conferences.