Your CSV is not fine.
Take for example the variant One Door 350 L 770 on line 31.
Based on its product_parent_id, it's the variant of the product S1.00002.01.001.2001 which is on line 3.
As far as I can see there are no other variants for that product.
If I look in the column Select Ironmongery: which is apparently a characteristic, I can see that you have the value '110 Degree Clip-Top - Blum' for the main product (that's the default value of the characteristic for that product). And in the variant, you have the value '110 Degree Clip-Top with integrated Blumotion - Blum'.
So you have AT LEAST two variants for that characteristic of that product. But in the CSV, you have filled only the information of one of the variants.
Thus, when you import, some data is missing. And when you have a variant without data, its stock is set to 0.
You should create one product with a characteristic via the interface and export it. You will see that you have one line for the main product data, and then one line per variant (and by the way, if the information is the same, you don't need to fill it in the variants).
Do the same in your CSV and it should work better.