Hi, first sorry for my english....
When I submit the Form, I receive the following message:
"This form has already been submitted"
The first Form could be sendet..... Starting from the second try, it dont work anymore... of course I made different inputs in the feelds, so it is not the same name or email... please can you help me? Thanks

It's by design. It prevents you from posting the form twice.
If you want to disable it, then open web/form/app/cls_ps_(table-name).inc.php
and comment out the following code.

//-- [BEGIN] Check PageSig
if ( !DEBUG_SKIP_DOUBLE_SUBMIT_CHECK )
{
	if ( !$this->sys->PageSig->Check( $pagesig_key ) )
	{
		$sc->DoubleSubmitError();
		break;
	}
}
//-- [END] Check PageSig

The result should look like

//-- [BEGIN] Check PageSig
//if ( !DEBUG_SKIP_DOUBLE_SUBMIT_CHECK )
//{
//	if ( !$this->sys->PageSig->Check( $pagesig_key ) )
//	{
//		$sc->DoubleSubmitError();
//		break;
//	}
//}
//-- [END] Check PageSig