How to program 2D jump 'n' run movement properly?

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C#

WPF

I want to program a 2D jump 'n' run like Super Mario Bros. in WPF. The code works so far, but the player-movement doesn't work like it should. I can't move when Mario is midair or when I am moving, i can't jump. I played around with Keyboard.IsKeyDown(e.Key), but there I loose all the momentum when I am trying to jump while I am moving. Is there any way to detect two keypresses at the same time?

Here would be my C# code:

What I have tried:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Windows.Threading;
using static System.Net.Mime.MediaTypeNames;

namespace Endless_Runner_Base
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {

        DispatcherTimer gameTimer = new DispatcherTimer();

        Rect playerHitBox;
        Rect groundHitBox;
        Rect obstacleHitBox;
        Rect goombaHitBox;

        bool jumping;

        int force = 20;
        int speed = 5;

        Random rnd = new Random();

        bool gameOver;

        double spriteIndex = 0;

        ImageBrush playerSprite = new ImageBrush();
        ImageBrush backgroundSprite = new ImageBrush();
        ImageBrush obstacleSprite = new ImageBrush();
        ImageBrush goombaSprite = new ImageBrush();

        int[] obstaclePosition = { 320, 310, 300, 305, 315 };

        int score = 0;
 




        public MainWindow()
        {
            InitializeComponent();

            myCanvas.Focus();

            gameTimer.Tick += GameEngine;
            gameTimer.Interval = TimeSpan.FromMilliseconds(20);

            backgroundSprite.ImageSource = new BitmapImage(new Uri("C:\\Users\\jho\\Desktop\\Visual Projekte\\trunk\\Endless Runner Base\\Endless Runner Base\\images\\background.gif"));
            background.Fill = backgroundSprite;
            background2.Fill = backgroundSprite;
            StartGame();

        }

        private void GameEngine(object? sender, EventArgs e)
        {
            

            if(Canvas.GetLeft(background) < -1024)
            {
                Canvas.SetLeft(background, Canvas.GetLeft(background2) + background2.Width);
            }

            if (Canvas.GetLeft(background2) < -1024)
            {
                Canvas.SetLeft(background2, Canvas.GetLeft(background) + background.Width);
            }

            Canvas.SetTop(player, Canvas.GetTop(player) + speed);
            
           
            
            scoreText.Content = "Score: " + score;


            playerHitBox = new Rect(Canvas.GetLeft(player), Canvas.GetTop(player), player.Width -15, player.Height);
            obstacleHitBox = new Rect(Canvas.GetLeft(obstacle) +10, Canvas.GetTop(obstacle), obstacle.Width, obstacle.Height);
            groundHitBox = new Rect(Canvas.GetLeft(ground), Canvas.GetTop(ground), ground.Width, ground.Height);


            if(playerHitBox.IntersectsWith(groundHitBox)) 
            {
                speed = 0;
                
                Canvas.SetTop(player, Canvas.GetTop(ground) - player.Height );
                
                jumping= false;

                spriteIndex += .5;

                if(spriteIndex > 4) 
                {
                    spriteIndex= 1;
                
                }
                RunSprite(spriteIndex);

            
            }

            if(jumping == true)
            {
                speed = -9;

                force -= 1;
            }
            else
            {
                speed = 12;
            }

            if (force < 0)
            {
                jumping= false;
            }

            if(Canvas.GetLeft(obstacle) < -50)
            {
                Canvas.SetLeft(obstacle, 950);

                Canvas.SetTop(obstacle, obstaclePosition[rnd.Next(0, obstaclePosition.Length)]);

                score += 1;
            }
            if (playerHitBox.IntersectsWith(goombaHitBox))
            {
                gameOver = true;

                gameTimer.Stop();
            }

            if (gameOver == true)
            {
                obstacle.Stroke = Brushes.Black;
                obstacle.StrokeThickness = 1;
                

                player.Stroke = Brushes.Red;
                player.StrokeThickness = 1;

                scoreText.Content = "Score: " + score + " Press ENTER to play again!!";
            }
            else
            {
                player.StrokeThickness= 0;
                obstacle.StrokeThickness= 0;
            }

        }

        private void KeyIsDown(object sender, KeyEventArgs e)
        {
             if (e.Key == Key.Enter && gameOver == true) 
            {
                StartGame();
                
            }
             if(e.Key == Key.Left)
            {
                if (Keyboard.IsKeyDown(Key.Space))
                {
                    Jump();
                }
                Canvas.SetLeft(background, Canvas.GetLeft(background) + 3);
                Canvas.SetLeft(background2, Canvas.GetLeft(background2) + 3);
                Canvas.SetLeft(obstacle, Canvas.GetLeft(obstacle) +12);
                Canvas.SetLeft(Goomba, Canvas.GetLeft(Goomba) + 12);
               
            }
             else if(e.Key == Key.Right)
            {
                if (Keyboard.IsKeyDown(Key.Space))
                {
                    Jump();
                }
                Canvas.SetLeft(background, Canvas.GetLeft(background) - 3);
                Canvas.SetLeft(background2, Canvas.GetLeft(background2) - 3);
                Canvas.SetLeft(obstacle, Canvas.GetLeft(obstacle) - 12);
                Canvas.SetLeft(Goomba, Canvas.GetLeft(Goomba) - 12);
              
            }
             else if(e.Key == Key.Space)
            {
                if (Keyboard.IsKeyDown(Key.Left))
                {
                    Canvas.SetLeft(background, Canvas.GetLeft(background) + 3);
                    Canvas.SetLeft(background2, Canvas.GetLeft(background2) + 3);
                    Canvas.SetLeft(obstacle, Canvas.GetLeft(obstacle) + 12);
                    Canvas.SetLeft(Goomba, Canvas.GetLeft(Goomba) + 12);

                }
                else if (Keyboard.IsKeyDown(Key.Right))
                {

                    Canvas.SetLeft(background, Canvas.GetLeft(background) - 3);
                    Canvas.SetLeft(background2, Canvas.GetLeft(background2) - 3);
                    Canvas.SetLeft(obstacle, Canvas.GetLeft(obstacle) - 12);
                    Canvas.SetLeft(Goomba, Canvas.GetLeft(Goomba) - 12);

                }
                Jump();
                
            }
        }

        private void Jump()
        {
            if (jumping == false && playerHitBox.IntersectsWith(groundHitBox))
            {
                jumping = true;
                force = 15;
                speed = -12;


                playerSprite.ImageSource = new BitmapImage(new Uri("C:\\Users\\jho\\Desktop\\Visual Projekte\\trunk\\Endless Runner Base\\Endless Runner Base\\images\\pixil-frame-1.png"));
            }
        }

        private void KeyIsUp(object sender, KeyEventArgs e)
        {
           
        }

        private void StartGame()
        {
            Canvas.SetLeft(background, 0);
            Canvas.SetLeft(background2, 1024);

            Canvas.SetLeft(player, 110);
            Canvas.SetTop(player, 140);

            Canvas.SetLeft(obstacle, 950);
            Canvas.SetTop (obstacle, 310);
            
            Canvas.SetLeft(Goomba, 300);
            Canvas.SetTop(Goomba, 310);
            RunSprite(1);

            goombaSprite.ImageSource = new BitmapImage(new Uri("C:\\Users\\jho\\Desktop\\vector-goomba-super-mario-bros-goomba-sprite-11563054676w6lknv0fmv.png"));
            obstacleSprite.ImageSource = new BitmapImage(new Uri("C:\\Users\\jho\\Desktop\\Visual Projekte\\trunk\\Endless Runner Base\\Endless Runner Base\\images\\obstacle.png"));
            obstacle.Fill = obstacleSprite;
            Goomba.Fill= goombaSprite;
            jumping = false;
            gameOver= false;
            score = 0;

            scoreText.Content = "Score: " + score;

            gameTimer.Start();

        }
        private void RunSprite(double i)
        {
            switch(i)
            {
                case 1:
                    playerSprite.ImageSource = new BitmapImage(new Uri("C:\\Users\\jho\\Desktop\\Visual Projekte\\trunk\\Endless Runner Base\\Endless Runner Base\\images\\pixil-frame-0.png"));
                    break;
                case 2:
                    playerSprite.ImageSource = new BitmapImage(new Uri("C:\\Users\\jho\\Desktop\\Visual Projekte\\trunk\\Endless Runner Base\\Endless Runner Base\\images\\pixil-frame-3.png"));
                    break;
               
               
               
            }
            player.Fill = playerSprite;
        }
    }
}