Newbie question
I understand most principles and still a few questions
Is is possible to add one page to more then 1 menu options , note it is about menu in the sidebar
Filternavigation for custom fields , as it is in most E commerce sites where vistors can filter on size , color , brand price
Hi and welkom in the world of Kirby 
ad 1: How do you get the other pages for the menu, and what kind of page (sibling, child) would you like to ad?
ad 2: Take a look at this blog article: Tags
About 1
I create a new page type , lets call it bikes
These gets custom fields , for example ,
gender —> men or women
E bike —> yes or no
Color —> black , white
Now i want the following menu
Header (gender)
women
men
Header (color)
white
black
a women back can be in gender (women) but also in color (white or black)
In both cases it is the same bike / page
Thats my idea
That goes hand in hand to what @tobiasweh posted.
Take a look at the “tagcloud” section . You can basically use multiple of these for each field (one for gender, one for color).
so what you mean i create a page with tag women and add this page to the sidebar
right ?
You add two fields named gender and color to each of the products/items, just like you wrote. Each of these can contain one value.
In your sidebar code, you can then pluck the used values out of the product pages and display them as links/buttons. You need two instances of the “tagcloud”, one that plucks the values from the gender field and one for the color field. Each of them can get a heading and be styled however you want.
By clicking on one of these links, the controller will then filter the displayed list by the selected value from the appropriate field. So one link will be /products/gender:women and the other /products/color:black. They can also be combined if you want: /products/gender:women/color:black.