- We need a matrix in the registration form. 4 colums and 4 rows is this possible?
With CSS, yes it's possible to move elements around anyway you like. More specifically CSS3. Aside from that I suppose you could try editing the PHP file of your CB default template to alter registration display, but you'd probably need to use REGEX to alter the field output as it's a single variable if you need HTML changes.
- Is there a possibillity to make fields, but hide them from the registration form, but get them shown if a user click on a plus ( image ) ?
If you make a plugin to do that, yes. There's CB Conditional, which conditional show/hides fields, but it doesn't show/hide based off a button click.
Pretty much both of your needs are very specific so CB obviously does neither out of the box and there's a huge probability you'll need to code such implementations your self.