How create Variant by csv importing

-- HikaShop version -- : 3.0.0
-- Joomla version -- : 3.6.5
-- PHP version -- : 7.0
-- Browser(s) name and version -- : Firefox

I'm trying to generate variant of some product on my website.
I use libre office to work on csv.
This is my step:
1) I create the main product with all the parameter
2) I generate 2 variants for example
3) I export the csv, so i can have an example
4) i add other variant adding row similar to the vaiants creted by hikashop, inserting in product_parent_id the product code of the main product
5) Import the csv.

Now i have a problem: i don't see the variants if i open a main product, and i don't see the variant finding by product code on the root.

If i try to export csv, i see all the variant created, but on product_parent_id column there are only "0" and no the value i wrote before.

Is that because i use thi particular product code for my Main products?

ex.
aaaaaa-bbbbb-qqqqqq
aaaaaa-bbbbb-wwwww
aaaaaa-bbbbb-yyyy

The caracter "-" create problem?

SOLVED:

When i upload csv, i delete before rows with main product, but it's a not good thing.

Now all works good. Thanks