XML tools context error

I am currently learning android development for a university module so I am sorry if this is a very basic error. I am currently just following this tutorial, understanding how android java differs to normal java and so on.

On the XML file activity_main I am getting the following error:

Cannot resolve symbol ${relativePackage}.${activityClass} Validates resource references inside Android XML Files

I have used Google and StackOverflow search to look at possible solutions, I found some articles stating it can be due to bad XML formatting which is where I believe the error is. I have also tried to run the project and it cant find the class file R. I have cleaned and rebuilt the project but the error continues to happen.

Here is my code if you would like to take a look. Although at the moment it is very similar to the tutorial website.

Any help is much appreicated, thank you

P.S I am using Android Studio