Display products from all subcategories

-- HikaShop version -- : HikaShop Business: 2.6.3
-- Joomla version -- : Joomla! 3.4.8 Stable [
-- PHP version -- : 5.4.45

Hi guys
Really like Hikashop an congratulate on great job making it.

I am working on a customers site (farming products) and he gave some requirements. We created a lot of product categories and subcategories with top 6 (displayed like main navigation on site). It is static part of the site and it wont change regarding on page user is at the moment. For that I used module Categories listing (list) and it works nice. I have created menu item Category display (izdelki) and it works as it should: displays subcategories and below them displays products that are directly in main category.

Now, what mu customer wants to accomplish:
1. When user click on a link to main category in main menu, he wants to see random products that are in all subcategories and in subsubcategories displayed as DIVs, without subcategories displayed in main area.
2. In side bar, we need module that will display list of subcategories (only first level) of main category. That list should be synchronized with category we are looking right now. (this one I managed to make it work creating another instance of category list module, but it synchronize only when clicked on a link in module itself, not from another module - main navigation).


3. On main page (index.php) we want to have one more list that will have links to different categories and/or subcategories. When clicked on link, it must show only PRODUCTS in specified category and its subcategories, not subcategories. Subcategories must be displayed as a list in module I was talking in second part of this question.


Now, I am figuring - there is a way to modify php files, but I am not so good in php and I could screw things. Is there some simply solution for this?

Hi again
I am still strugling with some navigation issues on this site and I need some advice about it.
We have manu sub-categories, up to 7th step down.

In order to make products more available to user (and skip all the clicking on subcategories), my client asked me to do next thing:
When you click on one of the 6 main categories you get all products from all levels of subcategories randomly displayed. Optionaly, first sublevel of categories should be displayed as a side menu. When you go to next level subcategory, that menu should be synchronized and shows subcategories from the level you are curently in, and so on.

Now, what I did:
As main display on my site I used "menu item - category listing" to display list of categories as list on top of the page and products from all subcategories.
Also I made module in sidebar for categories listing with synchronize option "on" and it works fine (showing categories from the level user is curently on).

But, when user gets to the last level subcategory or to the product page - module dissapears and also the category listing on top of the page. I need this to be displayed even on last level subcategory listing, even though it does not have any subcategories. In that case it should display listing for parent category of the curently displayed. It has to stay that way also when you get to the product page. Is there any way to achieve this.

P.S. I use generated URLs for breadcrumbs, so it is not an option for navigation through all subcategories on the store. For example, when user clicks on a product (that is placed in a 6th level subcategory) from category listing displaying the third level subcategory, breadcrumbs skips all steps between third and 6th level. I attached some images for clarity.

Thanx

Hi
I tried with protostar template, same thing happens.
here are screenshots of settings for menu listing I use as main view and for module listing (sidebar).