Form1.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Test_Alpha_govnokod_
{
    public partial class Form1 : Form
    {
        //Переменные
        string UserName;
        int QuestionNumber = 0;
        public int TrueAns;

        string[] questionsArray =
        {
            "Who are you?",
            "what's new"
        };
        int[] TrueAnsArray = {
            4, 2, 1, 3,
        };


        //Инициализация новой формы с логером
        Form2 logger = new Form2();
        //Инициализация 1-ой формы
        public Form1()
        {
            InitializeComponent();
            logger.Show();
            LoadAllQuestion(QuestionNumber);
        }   
        //Авторизация
        private void button1_Click(object sender, EventArgs e)
        {
            
            if (UserNameBox.Text == "")
            {
                logger.ButLog("Error:[Bad User Name!];");
            }
            else
            {
                UserName = UserNameBox.Text;
                string logmess = ("I: User: " + UserName + " was logged in successfully! ");
                //вызов метода со второй формы для вывода лога (временный метод)
                logger.ButLog(logmess);
                tabControl1.SelectTab(1);
                UserNameLabel1.Text = UserName;
                UserNameLabel2.Text = UserName;
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            tabControl1.SelectTab(2);
            string logmess = ("I: Frame was loaded in successfuly");
            logger.ButLog(logmess);

        }
       public void LoadAllQuestion(int QuestionNumber)
        {
            labelQuest.Text = questionsArray[QuestionNumber];
            TrueAns = TrueAnsArray[QuestionNumber];
        }

        private void NextQuestion_Click(object sender, EventArgs e)
        {
            int ButAns;
            if (checkBox1.Checked)
            {
                ButAns = 1;
            } else if (checkBox2.Checked)
            {
                ButAns = 2;
            } else if (checkBox3.Checked)
            {
                ButAns = 3;
            } else
            {
                ButAns = 4;
            }

            if (ButAns == TrueAns)
            {
                MessageBox.Show("true");
            }
            else
            {
                MessageBox.Show("false");
            }
            QuestionNumber++;
            LoadAllQuestion(QuestionNumber);
            checkBox1.Checked = false;
            checkBox2.Checked = false;
            checkBox3.Checked = false;
            checkBox4.Checked = false;
        }
    }
}