I don't know how to fix the error in the code.
Fn and ln in JavaClass Person
You don't need to write FN in the brackets.
Person p = new Person("Ali", "Ahmadi");
Maybe, you should look for some code samples. It's really helpful - also to learn some best-practices. Maybe codesamples like this.
Btw: Code Samples as image is... Providing the sample code with the editors "code sample" function would be nice.