Can somebody help me understand what is wrong with my code and why i have soo many errors

using System;
public static class Lab4_2
{
public static void Main()
{
const int PASS = 50;
int numPass = 0, numFail = 0, totalMarks = 0;
double mark, perPass = 0, perFail = 0;

    // loop to read in a valid mark or the sentinel value
    do
    {
        // Read initial mark (seed the loop)
        Console.Write("Enter a mark between 0 and 100 (-ve value to stop): ");
        mark = Convert.ToDouble(Console.ReadLine());
    } while (mark > 100);
    // if the inputted mark is not the sentinel value, process it

    while (mark >= 0)
    {

        // increment the counter for the total number of data values
        totalMarks++;

        // Determine if the mark is a pass or fail (If statement)
        if (mark >= 50)
            Console.WriteLine("PASS");
        else
            if (mark < 50)
            Console.WriteLine("Fail");

        // Read next mark
        Console.Write("Enter the next mark between 0 and 100 (-ve value stop)=>");
        mark = Convert.ToInt32(Console.ReadLine());
    } while (mark > 100) ;
}

    // Calculate the percentage of marks that were passes and fails
        if (totalMarks > 0)

	{
		perPass= numPass /(double) totalMarks;
        perFail= numFail /(double) totalMarks;
}

internal class totalMarks

{
else
{
perPass = 0;
perFail = 0;

// Print results
Console.WriteLine(“Total number of marks = {0}”, totalMarks);
Console.WriteLine(“Percentage of passing marks = {0:P1}”, perPass);
Console.WriteLine(“Percentage of failing marks = {0:P1}”, perFail);
Console.ReadLine();
}
}
}

Hello @script7949848547, welcome to the forums! What errors are you getting? It looks like, at a first glance, that you could have created an infinite loop.

im very lost with everything

Can you post the specific error messages, as well as a link to the exercise, please?