Every time I launch the project, it is only a black screen

Question

import UIKit
import CoreData
class KontakteTableViewController: UITableViewController {
   
    @IBOutlet var KontakteTableView: UITableView!
    
    var kontakteArray = [Kontakt]()
    var selectedKontakt: Kontakt?
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        KontakteTableView.delegate = self
        KontakteTableView.dataSource = self
        
       loadData()

        
    }
    @IBAction func addKontaktButton(_ sender: UIBarButtonItem) {
    }
    @IBAction func searchKontaktButton(_ sender: UIBarButtonItem) {
    }
    @IBAction func deleteAllButton(_ sender: UIBarButtonItem) {
    }
    
    func createKontakt()  {
        let alert = UIAlertController(title: "Add contact", message: nil, preferredStyle: .alert
        )
        alert.addTextField { (textField) in
            textField.placeholder = "Vorname"
        }
        alert.addTextField { (textField) in
            textField.placeholder = "Nachname"
        }
        alert.addTextField { (textField) in
            textField.placeholder = "Telefonnummer"
            textField.keyboardType = .numberPad
            
        }
        
    
    let action = UIAlertAction(title: "OK", style: .default) { (_) in
        if alert.textFields?[0].text?.count != 0 && alert.textFields?[1].text?.count != 0 &&  alert.textFields?[2].text?.count != 0  {
            
            
            let vorname = alert.textFields?[0].text
            let nachname = alert.textFields?[1].text
            let telefonnummer = Int64((alert.textFields?[2].text)!)
            
            
            
            
            
            // Core Data
            let kontakt = CoreDataService.defaults.createKontakt(_vorname: vorname!, _nachname: nachname!, _telefonnummer: telefonnummer!)
           
            
            // Array
            self.kontakteArray.append(kontakt)
            self.KontakteTableView.reloadData()
            
        } else {
            self.errorMessage(_message: "Bitte Daten angeben")
            
        }
    }
    alert.addAction(action)
        present(alert, animated: true, completion: nil)
    
 }

    func loadData() {
        let kontakteArray = CoreDataService.defaults.loadData()
        
        if let _kontakteArray = kontakteArray {
            self.kontakteArray = _kontakteArray
            self.KontakteTableView.reloadData()
        }
    
        
        
    }
    func errorMessage(_message: String) {
        let alert = UIAlertController(title: "Fehler", message: _message, preferredStyle: .alert)
        let okAction = UIAlertAction(title: "OK", style: .default) { (_) in }
            alert.addAction(okAction)
        present(alert, animated: true, completion: nil)
    }
    @objc func longPress(_ sender: UIGestureRecognizer) {
        if sender.state == UIGestureRecognizer.State.ended {
            let longPressLocationPoint = sender.location(in: self.KontakteTableView)
            
            if let pressIndexPath = self.KontakteTableView.indexPathForRow(at: longPressLocationPoint) {
                var task = UITextField()
                
                
                let alert = UIAlertController(title: "Änderung", message: "Neue Daten eingeben", preferredStyle: .alert)
                let action = UIAlertAction(title: "OK", style: .default) { (action) in
                    self.kontakteArray[pressIndexPath.row].telefonnummer = Int64(task.text!)!
                    self.KontakteTableView.reloadData()
                    CoreDataService.defaults.saveContext()
                
                }
                alert.addTextField { (textField) in
                    textField.placeholder = "Neue Telefonnummer"
                    textField.keyboardType = .numberPad
                    task = textField
                }
                let cancelAction = UIAlertAction(title: "Abbrechen", style: .default) { (_) in
                    
                }
                alert.addAction(action)
                alert.addAction(cancelAction)
                
                present(alert, animated: true, completion: nil)
            }
        }
    }
    
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "GoToKontakteInfo" {
            let destVC = segue.destination as! KontaktInfosViewController
            destVC.kontakt = selectedKontakt
        }
    }
    

}
extension KontakteTableViewController {

// MARK: - Table View DataSource

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return kontakteArray.count
    } // Zeile erstellen
    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath)
        
        let longPressRecognizer = UILongPressGestureRecognizer(target: self, action: #selector(longPress(_:)))
        cell.addGestureRecognizer(longPressRecognizer)
        
        let kontakt = kontakteArray[indexPath.row]
        
        cell.textLabel?.text = "Name: \(kontakt.vorname!) Alter: \(kontakt.nachname!) Telefonnummer: \(kontakt.telefonnummer)"
        return cell
    }

}

extension KontakteTableViewController {
    override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCell.EditingStyle, forRowAt indexPath: IndexPath) {
        if editingStyle == .delete {
            CoreDataService.defaults.deleteKontaktFromDataStack(indexPath: indexPath, kontakteArray: &kontakteArray)
            KontakteTableView.reloadData()
        }
    }
    
    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        selectedKontakt = kontakteArray[indexPath.row]
        
        performSegue(withIdentifier: "GoToUserInformationSeque", sender: nil)
        KontakteTableView.deselectRow(at: indexPath, animated: true)
        
    }
    
    
}

Answer 1

The problem may be in your storyboard. Select your first screen that you want to be presented and in the attributes inspector, check "Initial View Controller". Sometimes when I change around the storyboard this happens to me.