Is it possible to avoid users answering the same form multiple times?
Yes, only when the users have to login. Then you can select the option only one answer per user.
Sorry for the dutch
But the first red circle is for the option only persons in my organisation
The second red circle is only 1 answer peperson
Why would anyone want that? If you have an issue, and someone asks you to elaborate; they wouldn't be able to help further in the topic...