[TYPO3-mvc] How to reload a page with a form?

[Robert Schneider]

I have an own registration form which I want to reload if the data is 
not valid. The form uses the object, and the input fields the property 
attributes. With the first call no object is given, obviously, and all 
fields are empty. Now, if the page is reloaded, what do I have to do 
that the fields get refilled with the already entered data?

Do I have to use redirect or forward for loading the same page? How do I 
have to provide the arguments?

What I also would like to achieve is that some warn messages (array) 
gets displayed. How does this get realized?

If anyone could give me an example, please. It cannot be that difficult 
but I really don't get it work after hours by myself.

Thanks in advance (I'm off for the next two weeks)!
Robert