The specific file name you mentioned, "geen idee.nl2pkg" , translates from Dutch to "no idea.nl2pkg." This implies it is a custom roller coaster or theme park file created by a user, likely named jokingly or as a placeholder.
Click the or use the file browser to navigate to the location where you saved geen idee.nl2pkg . geen idee.nl2pkg
If you want to view how the coaster was made or modify the scenery: Open the . The specific file name you mentioned, "geen idee