Fatal error Declaration

Hi, I am having issues with my plugins and I can't figure out why it crash, here is the crash dump :

Error: Declaration of CupidonSauce173\BouncyBlocks\BouncyBlocks:nCommand(pocketmine\command\CommandSender $sender, pocketmine\command\Command $command, $label, array $args) must be compatible with pocketmine\plugin\PluginBase:nCommand(pocketmine\command\CommandSender $sender, pocketmine\command\Command $command, string $label, array $args): bool
File: BouncyBlocks_v1.1.phar/src/CupidonSauce173BouncyBlocks/BouncyBlocks
Line: 14
Type: E_COMPILE_ERROR
THIS CRASH WAS CAUSED BY A PLUGIN

Code:
[5] use pocketmine\command\Command;
[6] use pocketmine\command\CommandSender;
[7] use pocketmine\event\entity\EntityDamageEvent;
[8] use pocketmine\event\player\PlayerMoveEvent;
[9] use pocketmine\event\Listener;
[10] use pocketmine\math\Vector3;
[11] use pocketmine\Player;
[12] use pocketmine\plugin\PluginBase;
[13]
[14] class BouncyBlocks extends PluginBase implements Listener{
[15]
[16] private $max;
[17] private $blocks;
[18]
[19] public $fall;
[20] public $bounceVelocity;
[21] public $disabled;
[22]
[23] public function onEnable(){
[24] $this->getServer()->getPluginManager()->registerEvents($this, $this);

Backtrace:

PocketMine-MP version: 1.7dev #731 [Protocol 201; API 3.0.0-ALPHA11]
Git commit: 7dd834bca004241a3a4ab812edd6fb7053b27bd9
uname -a: Linux b1.cryoservers.com 3.10.0-693.11.6.el7.x86_64 #1 SMP Thu Jan 4 01:06:37 UTC 2018 x86_64
PHP Version: 7.2.1
Zend version: 3.2.0
OS : Linux, linux

Here is the code of my main :

<?php

namespace cupidonsauce173\BouncyBlocks;

use pocketmine\command\Command;
use pocketmine\command\CommandSender;
use pocketmine\event\entity\EntityDamageEvent;
use pocketmine\event\player\PlayerMoveEvent;
use pocketmine\event\Listener;
use pocketmine\math\Vector3;
use pocketmine\Player;
use pocketmine\plugin\PluginBase;

class BouncyBlocks extends PluginBase implements Listener
{

private $max;
private $blocks;

public $fall;
public $bounceVelocity;
public $disabled;

public function onEnable(){
$this->getServer()->getPluginManager()->registerEvents($this,$this);
$this->saveDefaultConfig();

$config = $this->getConfig();
$this->max = $config->get("max");
$this->blocks = $config->get("blocks");
$this->fall = new \SplObjectStorage();
$this->bounceVelocity = new \SplObjectStorage();
$this->disabled = new \SplObjectStorage();

}


Someone can help me ?

 

I just put the part of the code where they say that there is a error

 

Nvm, find the problem lol, forgot to add strings