Clean code of the first task.

src/main/java/view/FirefighterGrid.java

@@ -2,13 +2,11 @@ package view;
 
 import javafx.scene.canvas.Canvas;
 import javafx.scene.paint.Color;
-import javafx.util.Pair;
 import model.BoardElement;
 import util.Position;
-
 import java.util.ArrayList;
 import java.util.HashMap;
-import java.util.List;
+
 
 public class FirefighterGrid extends Canvas implements Grid<model.BoardElement>{