Help! I've been trying to fix this for too long.

Question

I'm getting the following error codes and have been struggling to fix them for quite some time now;
Assets\missionProgress.cs(9,10): error CS1513: } expected
Assets\missionProgress.cs(17,5): error CS8803: Top-level statements must precede namespace and type declarations.
Assets\missionProgress.cs(32,1): error CS1022: Type or namespace definition, or end-of-file expected

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class missionProgress : MonoBehaviour
{
// Start is called before the first frame update
void Start()
{
public Transform missionCheck;
public float missionDistance = 1f;
public LayerMask missionMask;
public int missionNext = 0;
}

// Update is called once per frame  
void Update()  
    {  
    missionStep = Physics.CheckSphere(missionCheck.position, missionDistance, missionMask);  

    if (missionStep == true)  
        {  
        missionNext =+ 1;  
        }  

    switch(missionNext)  
        {  
        case 1:  
           Destroy(m1, 1);  
        }  
    }  

}

Answer 1

so little code, so many errors,

1) you can not define properties inside a function:

void Start()
{
public Transform missionCheck;
public float missionDistance = 1f;
public LayerMask missionMask;
public int missionNext = 0;
}

2) variables must be defined before used:

missionStep =   

3) object property used without allocating object (missionCheck.position)

missionStep = Physics.CheckSphere(missionCheck.position, missionDistance, missionMask);

4) case statements in a switch must have a break