Hi @Altin - generally speaking: anyone invited to a file/prototype will be able to invite other users (such as guests) on it at the same permission level.
For example, if someone has “can view” permissions on a file, they’ll only be able to invite other users with can view permissions. If you have edit access on a file, you’ll be able to invite other users with edit or view access.
If you are on an org or enterprise plan, you’ll have the ability to manage public link sharing more specifically in the way I think you’re looking for: https://help.figma.com/hc/en-us/articles/5726756336791-Manage-public-link-sharing-and-open-sessions
I see you filed a support ticket. Since I’m unable to see your type of plan and provide a more tailored response, support will reach back out to you via email with specific in your situation.