ASP.Net Form send click but nothing happens

I am building a german payment provider into my site.

But when I click on "Submit", nothing happens. I think I've looked at it too much and I can't see the forest for the trees any more...

        <form method="post"  action="https://www.sofortueberweisung.de/payment/start">
            <input name="currency_id" type="hidden" value="EUR" />
            <input name="reason_1" type="hidden" value="Zambuu" />
            <input name="user_id" type="hidden" value="29593" />
            <input name="project_id" type="hidden" value="80145" />
            <input type="submit" value="Absenden" />
        </form>

Update

Okay, so it's a little bit unclear what I want, it seems:

I have a lot of asp-sites already, and now I must send, however, the information that is given by the hidden inputs by post-method to the site "sofortüberweisung.de/payment/start".

However I can solve it, it's not necessary, there is no need for a form-tag, if there is another solution (e.g. with the code behind).

So: How can I send a lot of post information (these here is only an example, in the real site there are a lot more) with code and redirect it to the right site?

If the code you have provided is within a standard ASP.NET form, so that you have nested form tags, try the solutions provided to this Stack Overflow question.

If it is possible to have this page be a simple html form, that is another possible solution.