You can link to a form from your Yapp app.
To start, create a survey or form on the survey tool of your choice.
Here are some options but you are not limited to:
Google Forms - free, but will require users to log in to a Google account if file uploads are required.
Once you have created your form, use the following steps for the easiest way to link it from your Yapp app:
Add a new page to your app and select Rich Text. You can also use any Rich Text document (like in a description of a session or a person).
Add a button to your new Rich Text document and enter your form URL into the Button Link
Save the page and publish your app!
When users tap your survey button, they will be redirected to the form. Their response will be recorded in the tool you used to create the survey.