added GridBagLayout and functionality for buttons after winning

src/main/java/Gui/ActionHandler.java

@@ -22,6 +22,12 @@ public class ActionHandler implements ActionListener {
 			restartGame.startGame();
 		}
 		
+		if (e.getSource() == GameGui.RestartBtn1) {
+			GameGui.questionNr = 0;
+			GameGui.WinningPanel.setVisible(false);
+			restartGame.startGame();
+		}
+		
 	}
 
 }

src/main/java/Gui/GameGui.java

@@ -77,18 +77,23 @@ GridBagConstraints gbc;
 		GameGui.MainPanel.setVisible(false);
 		GameGui.ButtonPanel.setVisible(false);
 		
+		GridBagConstraints gbc = new GridBagConstraints();
+		
 		RestartBtn1 = new JButton("Nochmal Spielen");
 		ClosingBtn = new JButton("Schliessen");
 		
-		WinningPanel = new JPanel(new GridLayout());
+		WinningPanel = new JPanel();
+		WinningPanel.setLayout(new GridBagLayout());
 		WinningLabel = new JLabel("Du hast Gewonnen!");
 		WinningLabel.setVerticalAlignment(JLabel.CENTER);
 		WinningLabel.setHorizontalAlignment(JLabel.CENTER);
 		WinningLabel.setFont(new Font("Serif", Font.BOLD, 28));
 		
-		WinningPanel.add(WinningLabel);
-		WinningPanel.add(RestartBtn1);
-		WinningPanel.add(ClosingBtn);
+		WinningPanel.add(WinningLabel,gbc);
+		WinningPanel.add(RestartBtn1,gbc);
+		WinningPanel.add(ClosingBtn,gbc);
+		RestartBtn1.addActionListener(new ActionHandler());
+		ClosingBtn.addActionListener(new ActionHandler());
         gui.Frame.add(WinningPanel);
 	}