Creating a form where users can edit their own submissions
In the 
Home » Administration » Structure
and in the content type
add new content type and create your forms as you need 

You can edit every content type i.e. node and 
for editing own submissions you can set appropriate permissions like 'edit own content' in the 
Home » Administration » People  under permissions tab

For multistep forms
you can in the hook_form_alter() create 

$form['redirect'] = 'your_next_form_path';

By using redirect as soon as the form is submitted you will be redirected to other form (only thing is proper path for node or form needs to be mentioned).