private void userControlTS_UserKeyPressed (object sender, KeyboardEventArgs e)
        {
            
            //Focus auf textBox in Form1 funktioniert wunderbar, aber ich will die Textbox in Form2 fokusieren
            textBox1.Focus();
                     
            //Taste an focusiertes Fenster schicken
            SendKeys.Send(e.KeyboardKeyPressed);
        }

private void userControlTS_UserKeyPressed (object sender, KeyboardEventArgs e)
        {
            //Kein Focus in Form2
            FormBrowser browser = new FormBrowser();
            browser.textBoxURL.Focus();
                     
            //Taste an focusiertes Fenster schicken
            SendKeys.Send(e.KeyboardKeyPressed);
        }

private void FormBrowserSteuerung_Load(object sender, EventArgs e)
        {
            FormBrowser browser = new FormBrowser();
            browser.Show();
        }

SendKeys.Send(e.KeyboardKeyPressed);

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        Form2 frm2 = new Form2();

        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            frm2.Show();            
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }
    }
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Form2 : Form
    {
        

        public Form2()
        {
            InitializeComponent();
        }

        private void Form2_Load(object sender, EventArgs e)
        {
            textBox1.Focus();
        }
    }
}

public FormBrowserSteuerung()

        FormBrowser browser = new FormBrowser();
        
        private void userControlTS_UserKeyPressed (object sender, KeyboardEventArgs e)
        {
            browser.textBoxURL.Focus();
            SendKeys.Send(e.KeyboardKeyPressed);
            
        }

        private void FormBrowserSteuerung_Load(object sender, EventArgs e)
        {
            browser.Show();
            browser.textBoxURL.Focus();
        }