Hi Marco.
If I’m understanding you correctly and you want to stop certain custom fields from displaying then you will probably want to modify your custom single.php template a little. If you aren’t sure of how to do this, please refer to:
The basic idea would be to find the code that prints out custom/additional fields, which looks like this and replace it with code that ignores the field (or fields) you specify, something like this.
You would of course have to change the value of $ignore to whatever is appropriate in your case. Hope that helps 🙂