Modifying assignment details such as instructions, due dates, or attached resources.
Hi RhonanMokriski,
Thank you for posting your question in this community.
In Microsoft Forms, there is an limitation which the maximum characters per question in up to 4,000 characters (Include space). That would be a reason why your students will be stopped typing around 800 words in their long answer.
For your information:
Form, question, response, and character limits in Microsoft Forms
I am afraid there is no out of box way to break this character limitation at this moment. If you have to use Quiz to collect the essay responses and document file can be considered. You can add an File Upload question in your quiz so that your student can upload document type file.
For your information:
Add questions that allow for file uploads
In this scenario, you can still review and mark the question in Microsoft Forms. You can review the student essay file by clicking on the file in Forms which it will be opened in Word for the web application for your to review.
Best regards,
Dihao