with some girls , if i buy it to see her video's and her photo's... the page said : buy an xxx video to unlock this video.
So i was searching how to buy an xxx video but i can't find it.
Can someone tell me how i can do that?

I do not know what "...buy an xxx video." is but, to buy an xxx card look for the triple red x's on the card. You can also click on 'Girls Store' / 'collections'. After buying card, go to your settings / advanced page and make sure your xxx shows are enabled. (note: xxx cards have sound)
Hope this helps.

I think I know the explanation: The videos of a model are free is you own at least one card from a model. However, the XXX videos are free only if you own an XXX card. However, to make matters worse XXX cards don't appear in the Girl's until you enable them in Advanced Setting.

So, for example, to get the free XXX videos of Lucy Li you must first but one of her 7 XXX cards.