Another thing about the Next and Previous option
 

I have a category, let´s call it Beauty

1-In the category Beauty I have 10 products
2-When I click on the first product I want to use the Next and Previous option to navigate forward.

In reviews post that doesn´t seems to be the case. I´m I misunderstanding something?
Se it for yourself: Gelé - My Product Gallery
This category contains 7 images. Click on the first product and try to navigate forward.

Okay in showphoto.php this block of code there is ORDER BY date DESC. what happens if you switch DESC to ASC

If i´m right, there is 4 lines with ORDER BY date DESC in showphoto.php
Should i change all 4 lines to ORDER BY date ASC?

In that code block yes try that.