Player Disconnect:

    @EventHandler
    public void handlePlayerDisconnect(PlayerDisconnectEvent event) {
        final ProxiedPlayer player = event.getPlayer();
        final FriendsData friendsPlayer = this.ventoxyCord.getFriendsManager().getCachedFriendsData().get(player.getName());

        for (String allFriendsUUIDs : friendsPlayer.getFriends()) {
            ProxiedPlayer allFriendsAsPlayer = ProxyServer.getInstance().getPlayer(UUID.fromString(allFriendsUUIDs));
            friendsPlayer.getFriends().stream().filter(s -> allFriendsAsPlayer != null).forEach(onlinePlayer -> ProxyServer.getInstance().getPlayer(UUID.fromString(onlinePlayer)).sendMessage(TextComponent.fromLegacyText(Prefix.getFriendsPrefix() + "§e" + player.getName() + " §7ist nun §c§loffline§8.")));
        }

        System.out.println(player.getUniqueId().toString());

        this.ventoxyCord.getBackendManager().getBungeePlayer(player.getUniqueId().toString(), bungeePlayer -> {
            final long onlineTime = System.currentTimeMillis() - this.ventoxyCord.getOnlineTimeManager().getOnlineTimeCache().get(player.getUniqueId().toString());

            Gson gson = new GsonBuilder().setPrettyPrinting().create();
            System.out.println(gson.toJson(friendsPlayer));

            bungeePlayer.setFriendsData(friendsPlayer);
            bungeePlayer.setPlaytime(bungeePlayer.getPlaytime() + onlineTime);

            System.out.println(gson.toJson(bungeePlayer.getFriendsData()));

            System.out.println(gson.toJson(bungeePlayer));

            this.ventoxyCord.getBackendManager().updatePlayer(bungeePlayer, (updateResult, throwable) -> ProxyServer.getInstance().getConsole().sendMessage("success"));
        });
    }

Update Methode:

    public void updatePlayer(final VentoxyPlayer ventoxyPlayer, final SingleResultCallback<UpdateResult> callback) {
        if (ventoxyPlayer == null)
            throw new NullPointerException("null");

        this.mongoDB.getPlayerCollection().replaceOne(Filters.eq("uuid", ventoxyPlayer.getUuid()),
                gson.fromJson(gson.toJson(ventoxyPlayer), Document.class), callback);
    }