So when I move I can fly but I don't to fly. I want my movement on the y-axis to remain constant. How do i do this?

void CubeTranslation()

{
    if (MoveLeft)
    {
        //CubeX += -0.5f;
        //movement.x += -0.5f;
        transform.Translate(Vector3.left * (10) * Time.deltaTime);

    }

    if (MoveRight)
    {
        //CubeX += 0.5f;
        //movement.x += 0.5f;
        transform.Translate(Vector3.right * (10) * Time.deltaTime);

    }

    if (MoveDown)
    {
        // CubeX += 0.3f;
        //CubeZ += -0.3f;
        //movement.z += -0.3f;
        transform.Translate(Vector3.back * (10) * Time.deltaTime);

    }

    if (MoveUp)
    {
        // CubeX += 1.3f;
        //CubeZ += 0.3f;
        //movement.z += 0.3f;
        //ToTranslate = true;
        transform.Translate(Vector3.forward * (10) * Time.deltaTime);
    }
    if (RotateLeft)
    {
        controllingObject[0].transform.Rotate(Vector3.left * 1.2f * Input.GetAxis("Mouse Y"));
        //controllingObject[0].transform.TransformDirection(Vector3.left);
        
        //controllingObject[0].transform.Rotate(Vector3.left * 1.2f);
        //controllingObject[1].transform.Rotate(Vector3.left * 1.2f);
    }
    if (RotateRight)
    {
        //controllingObject.transform.Rotate(Vector3.right * 1.2f);
        controllingObject[0].transform.Rotate(Vector3.right * -1.2f * Input.GetAxis("Mouse Y"));
        //controllingObject[0].transform.TransformDirection(Vector3.right);

    }

    if (RotateUp)
    {
         controllingObject[0].transform.Rotate(Vector3.up * 1.2f * Input.GetAxis("Mouse X"));
         
    }
    if (RotateDown)
    {
        
        controllingObject[0].transform.Rotate(Vector3.down * -1.2f * Input.GetAxis("Mouse X"));
    }

   
    transform.rotation = Quaternion.Euler(transform.eulerAngles.x, transform.eulerAngles.y, 0);

change this at Line 33

 transform.Translate(Vector3.forward * (10) * Time.deltaTime);

to this

 transform.Translate(new Vector3((Vector3.forward.x,0,Vector3.forward.z)(10) * Time.deltaTime);

Figured it out on own.