I just dont understand the problem. I filled in my wordpress username and password. But it wont work.
No you don’t have to use WordPress user name and password but SMTP server details as described on the following pages.
If you find it’s hard to configure SMTP settings then instead use WP-mail send method as shown in the attached screenshot.
No, i dont get other emails.
Then it is not contact form problem but your site problem that you need to troubleshoot and resolve.
You can troubleshoot the email issue as described on the following pages or contact your web host regarding this.