Products not showing anymore and 2 more questions

I got 3 things that makes me run in circles.

-1-
I tried to look anywhere but I must have done some wrong.
I can go to the frontside hikashop and click the categories and the categories overview, but when I reach the last categorie of the tree where the product should appear I get an empty page.
The products are all there in the database. I can if I know the direct link get to see a product, just not the overview of products in a category.
Only the carrousel shows products.

-2-
Also I managed to vanish the button go to shopchart. I have the cart in a module on the right, I can delete products from the chart, but I can't go to the chart to finalize the thing. How will I get a link/button back to go to the chart? Did I switch off someting?

-3-
How can I get the euro sign in front of the amount, and how can I give the div's in a category and product overview a fixed hight. (And will these changes then stay with a future upgrade of hikashop?)

1. I think that you have not well configured the module displaying the categories. In these hikashop options select "Products Listing" for the option "Menu".

2. By default you should have this button displayed. Please check if the option "Show proceed button in the cart" is enabled in the cart module options.

3. To place the euro sign before the amount, you can do it in the currencies options (System > Currencies), edit the euro currency.

For the fixed height, you can do this by CSS. Here is some documentation:
www.hikashop.com/fr/support/documentation/faq.html#css

Thanks Xavier, 2 and 3 got solved.
But point 1 I do not understand. I changed nothing in the menu.
Basically I have 1 button that goes to the top category listing. You get nicely all the categories in the 'root'. From there you click one in the list and you get nicely shown the subcategories.
But from here some changed. when I click one of these sub categories it would show me all the products in it. But atm I get a blanc page. And I really can't think of what I might have switched on or off. Defenitly not someting in the main menu?! But then what is it?