strange behavior in back-end

-- HikaShop version -- : 2.6.4
-- Joomla version -- : 3.6.4

Hello, 2 question about back-end.
1) in the first image there is category colory, red underlined, I dont know how I made it but now i dont know how to delete it, couse if i select the root I see other category but not that.

2)This is very strange things, in prduct view If I select the category "Aghi" I see 3 subcategory (second image) with no subcategory, but if I slect the category "Aghi cartuccia crystal" (3rd image ) by the graph it seems there is other subcategory, even if that category doesn't have any subcateogry.
Why that?? it is very strange I just noted today

Thanks
FRank

Hello
I installed hikashop after downloaded, and I make the rebuilding in the category, but I am worried about the situation now
the tree is changed again and I think not in better, you can see the image.
And now it has other strange behavior, when I click on the last child category, it show the product but the tree closes completely, while before it keeps opening the last category.

I am very worried
Thanks
Frank

From phpmyadmin the category root has parent_category_id=55 so I have to change that in "0" Right.
About the category color I have two of them, the first in the tree has parent_category_id =0 and the second one has parent_category_id =2
So I have to change the first one into "1"
And after having changed them i have to rebuild.
Did I understand good?

Thanks
Frank

Hello
I think it is solved, just to be sure Can you check in the image the category tree is correct please, particularry the system category such as "Stato Ordine", "Categorie I.V.A" etc. and if something miss.

Thanks
Frank