I'm very confused here. I'm just Plain out lost can anyone guide me a bit and tell me where I'm going wrong

class Student {
    constructor(gpa, credits){
        this.gpa = gpa;
        this.credits = credits;
    }
    set major(major) {

      if(this.gpa === 'Junior' || this.gpa === 'Senior'){
        this._major = this.major;
      } else {this._major = major;}

    }


    stringGPA() {
        return this.gpa.toString();
    }

    get level() {
        if (this.credits > 90 ) {
            return 'Senior';
        } else if (this.credits > 60) {
            return 'Junior';
        } else if (this.credits > 30) {
            return 'Sophomore';
        } else {
            return 'Freshman';
        }
    }
}

var student = new Student(3.9, 60);