Can't add script behaviour AssemblyInfo.cs. The script needs to derive from MonoBehaviour!

I’ve just started to use Unity but every-time I create any script and try to attach it to an object I get hit with
Can’t add script behaviour AssemblyInfo.cs. The script needs to derive from MonoBehaviour!
I have been stuck for hours and searched almost every page but still hasn’t solved my issue

I’m following this tutorial on YouTube

I noticed I was in an older version of unity to I just installed the latest and that seemed to fix it, thanks for the response

Maybe the script doesnt need to go into the scene, AssemblyInfo should just be…information about your assembly. Version number, application name, etc. Does this error only happen while adding the script to the scene? And if leaving the script out, does it affect desired behavior? Make a backup of the script outside of your project, and try deleting the original to see what happens.

Do you have a file called AssemblyInfo.cs somewhere?