BedWars - Teamboxes

After a little testing of code, I now have a new problem: The inventory is only called when you click with an item on the end box. Another problem is that the items are still in the box after being taken out and have doubled. If someone can help me please write privately or write a suggestion here as a thread.
Thank you!

Information: The teams are ArrayLists

Code:

//Variables

    public static HashMap<String, List<ItemStack>> teamboxblau = new HashMap<>();
    public static HashMap<String, List<ItemStack>> teamboxgelb = new HashMap<>();
    public static HashMap<String, List<ItemStack>> teamboxgrün = new HashMap<>();
    public static HashMap<String, List<ItemStack>> teamboxrot = new HashMap<>();

    public static List<ItemStack> a = new ArrayList<ItemStack>();

//InteractEvent

                    if(e.getClickedBlock() == null) {
                        return;
                    }
                    if(e.getClickedBlock().getType() != Material.ENDER_CHEST) return;
                  
                    e.setCancelled(true);
                  
                  
                    if(Main.teamblau.contains(p)) {
                      
                      
                        Inventory blau = Bukkit.createInventory(null, 27, "§5Teamchest");
                      
                        List<ItemStack> is = Main.teamboxblau.get("teamblau");
                      
                        if(is == null) {
                          
                            p.openInventory(blau);
                            return;
                          
                        }
                      
                        for(ItemStack i : is) {
                            if(i != null) {
                                blau.addItem(i);
                            }
                        }
                      
                        p.openInventory(blau);
                      
                      
                    }

//InventotyCloseEvent

                if (Main.teamblau.contains(p)) {

                    ItemStack[] is = e.getInventory().getContents();

                    for (ItemStack i : is) {
                        Main.a.add(i);
                    }

                    Main.teamboxblau.put("teamblau", Main.a);

                }

//

Are there serios mistakes in there?