ios application icon hangs on app startup

After clicking on the application icon, it remains down for a while (~ 2 sec), and then run the application. It feels that the main thread hangs (UI Thread). Help solve the problem!

import UIKit
import Fabric
import Crashlytics
import VK_ios_sdk
import FBSDKCoreKit
import FBSDKLoginKit
import GoogleMaps

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

var window: UIWindow?


func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
    // Override point for customization after application launch.

    Fabric.with([Crashlytics.self])
    GMSServices.provideAPIKey(GPROJ_KEY)

    //DataService.ds.REF_BASE.unauth()

    return FBSDKApplicationDelegate.sharedInstance().application(application, didFinishLaunchingWithOptions: launchOptions)
}

@available(iOS 9.0, *)
func application(app: UIApplication, openURL url: NSURL, options: [String : AnyObject]) -> Bool {
    FBSDKApplicationDelegate.sharedInstance().application(app, openURL: url, sourceApplication: options[UIApplicationOpenURLOptionsSourceApplicationKey] as! String, annotation: [UIApplicationOpenURLOptionsAnnotationKey])
    VKSdk.processOpenURL(url, fromApplication: options[UIApplicationOpenURLOptionsSourceApplicationKey] as! String)
    return true
}

@available(iOS 8, *)
func application(application: UIApplication, openURL url: NSURL, sourceApplication: String?, annotation: AnyObject) -> Bool {
    FBSDKApplicationDelegate.sharedInstance().application(application, openURL: url, sourceApplication: sourceApplication, annotation: annotation)
    VKSdk.processOpenURL(url, fromApplication: sourceApplication)
    return true
}

func applicationWillResignActive(application: UIApplication) {
    // Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
    // Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
}

func applicationDidEnterBackground(application: UIApplication) {
    // Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
    // If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
}

func applicationWillEnterForeground(application: UIApplication) {
    // Called as part of the transition from the background to the inactive state; here you can undo many of the changes made on entering the background.
}

func applicationDidBecomeActive(application: UIApplication) {
    FBSDKAppEvents.activateApp()
}

func applicationWillTerminate(application: UIApplication) {
    // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
}

func application(application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: NSData) {

    var oldDeviceToken = NSUserDefaults.standardUserDefaults().stringForKey("deviceToken")

    if oldDeviceToken == nil {
        oldDeviceToken = ""
    }

    let tokenChars = UnsafePointer<CChar>(deviceToken.bytes)
    var tokenString = ""

    for i in 0..<deviceToken.length {
        tokenString += String(format: "%02.2hhx", arguments: [tokenChars[i]])
    }


    if oldDeviceToken != tokenString {
        removeOldToken(oldDeviceToken)
    }

    registerForRemoteNotifications(tokenString)


}
}

I use the listeners to real-time database (Firebase) throughout the hole application. Maybe I forgot to remove some of them and i became a memory leak? But in any case the application has been deleted from the memory ..