diff --git a/ManagerService/Controllers/ConfigurationController.cs b/ManagerService/Controllers/ConfigurationController.cs
index 841c0ad..edd9a96 100644
--- a/ManagerService/Controllers/ConfigurationController.cs
+++ b/ManagerService/Controllers/ConfigurationController.cs
@@ -23,14 +23,16 @@ namespace ManagerService.Controllers
         private ConfigurationDatabaseService _configurationService;
         private SectionDatabaseService _sectionService;
         private ResourceDatabaseService _resourceService;
+        private DeviceDatabaseService _deviceService;
         private readonly ILogger<ConfigurationController> _logger;
 
-        public ConfigurationController(ILogger<ConfigurationController> logger, ConfigurationDatabaseService configurationService, SectionDatabaseService sectionService, ResourceDatabaseService resourceService)
+        public ConfigurationController(ILogger<ConfigurationController> logger, ConfigurationDatabaseService configurationService, SectionDatabaseService sectionService, ResourceDatabaseService resourceService, DeviceDatabaseService deviceService)
         {
             _logger = logger;
             _configurationService = configurationService;
             _sectionService = sectionService;
             _resourceService = resourceService;
+            _deviceService = deviceService;
         }
 
         /// <summary>
@@ -197,6 +199,16 @@ namespace ManagerService.Controllers
 
                 _configurationService.Remove(id);
 
+                // Delete config for all devices
+                List<Device> devices = _deviceService.GetAllWithConfig(id);
+
+                foreach (var device in devices)
+                {
+                    device.Configuration = null;
+                    device.ConfigurationId = null;
+                    _deviceService.Update(device.Id, device);
+                }
+
                 MqttClientService.PublishMessage($"config/{id}", JsonConvert.SerializeObject(new PlayerMessageDTO() { configChanged = true, isDeleted = true }));
 
                 return new ObjectResult("The configuration has been deleted") { StatusCode = 202 };
diff --git a/ManagerService/Controllers/SectionController.cs b/ManagerService/Controllers/SectionController.cs
index 714dfef..5b4e1e9 100644
--- a/ManagerService/Controllers/SectionController.cs
+++ b/ManagerService/Controllers/SectionController.cs
@@ -65,9 +65,14 @@ namespace ManagerService.Controllers
                 if (id == null)
                     throw new ArgumentNullException("Param is null");
 
-                List<Section> sections = _sectionService.GetAllFromConfiguration(id);
+                if (_configurationService.IsExist(id))
+                {
+                    List<Section> sections = _sectionService.GetAllFromConfiguration(id);
 
-                return new OkObjectResult(sections.Select(r => r.ToDTO()));
+                    return new OkObjectResult(sections.Select(r => r.ToDTO()));
+                }
+                else
+                    return new NotFoundObjectResult("Configuration not found");
             }
             catch (ArgumentNullException ex)
             {
diff --git a/ManagerService/Extensions/MqttClientService.cs b/ManagerService/Extensions/MqttClientService.cs
index a13ba88..3ea84c4 100644
--- a/ManagerService/Extensions/MqttClientService.cs
+++ b/ManagerService/Extensions/MqttClientService.cs
@@ -5,6 +5,7 @@ using MQTTnet.Client;
 using MQTTnet.Client.Connecting;
 using MQTTnet.Client.Disconnecting;
 using MQTTnet.Client.Options;
+using MQTTnet.Protocol;
 using Newtonsoft.Json;
 using System;
 using System.Collections.Generic;
@@ -135,8 +136,9 @@ namespace Mqtt.Client.AspNetCore.Services
             var mqttMessage = new MqttApplicationMessageBuilder()
                 .WithTopic(topic)
                 .WithPayload(message)
-                .WithExactlyOnceQoS()
-                .WithRetainFlag()
+                .WithAtMostOnceQoS()
+                .WithQualityOfServiceLevel(MqttQualityOfServiceLevel.AtMostOnce)
+                .WithRetainFlag(false)
                 .Build();
 
             if (mqttClient.IsConnected)
diff --git a/ManagerService/Services/DeviceDatabaseService.cs b/ManagerService/Services/DeviceDatabaseService.cs
index 766340c..da39b09 100644
--- a/ManagerService/Services/DeviceDatabaseService.cs
+++ b/ManagerService/Services/DeviceDatabaseService.cs
@@ -29,6 +29,11 @@ namespace Manager.Services
             return _Devices.Find(d => d.Connected).ToList();
         }
 
+        public List<Device> GetAllWithConfig(string configId)
+        {
+            return _Devices.Find(d => d.ConfigurationId == configId).ToList();
+        }
+
         public Device GetById(string id)
         {
             return _Devices.Find<Device>(d => d.Id == id).FirstOrDefault();