28.07 20:37:17 [Server] INFO Fatal error: Declaration of MiniBosses\Main::onCommand(pocketmine\command\CommandSender $sender, pocketmine\command\Command $cmd, $label, array $args) must be compatible with pocketmine\plugin\PluginBase::onCommand(pocketmine\command\CommandSender $sender, pocketmine\command\Command $command, string $label, array $args): bool in /plugins/MiniBosses-master/src/MiniBosses/Main.php on line 28
28.07 20:37:17 [Server] INFO Fatal error: Declaration of MiniBosses\Main::onCommand(pocketmine\command\CommandSender $sender, pocketmine\command\Command $cmd, $label, array $args) must be compatible with pocketmine\plugin\PluginBase::onCommand(pocketmine\command\CommandSender $sender, pocketmine\command\Command $command, string $label, array $args): bool in /plugins/MiniBosses-master/src/MiniBosses/Main.php on line 28
and please update to 3.0.0