Check your validations, one of them validates the given grade for averageGrade > 4.5 && averageGrade >= 5.5:

        else if (incomeSalary < minimalSalary && averageGrade > 4.5 && averageGrade >= 5.5 && socialScholarShip > excellentResultsScholarship)

compare with C# variant of validation:

            if (gradeAverage >= 5.5 && income < minimumIncome)
            {
                if (stipendium > gradeMultiplier)
                {
                    Console.WriteLine($"You get a Social scholarship {stipendium} BGN");
                }
                else if (stipendium < gradeMultiplier)
                {
                    Console.WriteLine($"You get a scholarship for excellent results {gradeMultiplier} BGN");
                }
                else if (stipendium == gradeMultiplier)
                {
                    Console.WriteLine($"You get a scholarship for excellent results {gradeMultiplier} BGN");
                }
            }
            else if (gradeAverage >= 5.5 && income >= minimumIncome)
            {
                Console.WriteLine($"You get a scholarship for excellent results {gradeMultiplier} BGN");
            }
            else if (gradeAverage > 4.5 && income < minimumIncome)
            {
                Console.WriteLine($"You get a Social scholarship {stipendium} BGN");
            }
            else
            {
                Console.WriteLine("You cannot get a scholarship!");
            }