thank you very much i solved it in a different way
I solved it the easier way using cefsharp
code :
browser.ExecuteScriptAsync("document.getElementById('join_neu_email_field').value ='aa';");
browser.ExecuteScriptAsync("document.getElementById('join_neu_password_field').value ='aa';");
When you say thank you for your help I will try it, I will use whichever is more comfortable