Problem with import csv

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Hello!
I had two problems:
1. when exporting goods from csv (I updated the prices and existence) existence of goods increased by eight times that is if in csv there was an existence 10, in shop shows existence 80. I can't understand in what the reason, and in manual to interrupt - it is very labor-consuming. In the previous time when updated these parameters, everything was as it should be. Very much I ask to give help.
2. When updating there is a strange thing: there are categories which, I removed long ago, and some goods which once entered these remote categories - again become attached to them. Of course it is possible to remove manually unnecessary and to pereprivyazat goods, but five, in the future I will have new categories and new goods and if I delete something, the volume of handwork will grow several times. I can't understand in what business. Thanks in advance.

Hello, Nicolas!
I thank you that responded on my request.
At first I will tell shortly about an order of the actions:
1. I do export of goods.
2. In the received file I (am applied) for dough changed quantity of all goods on "1", saved this file.
3. Import from this file.
The quantity turned out incorrect (not such as I stated it in the csv file is it is visible on the enclosed picture). Also categories were added new (and were duplicated), appeared without name. Goods appeared too without name.
Problems which I want to solve is:
1. Incorrect quantity, not what I brought in csv.
2. Emergence of new categories (similar on existing) which wasn't before import.
From the heart I thank you in advance for the help as I am going to get the HikaShop business version, but before it I want to deal with all that to me is unclear. Business the version is necessary to me for use of functions which are provided by the paid version. Very much I hope for your help!

Hello, dear Nicolas!
I now try to solve the problem means available to me. Of course my attempts are experimenting. Here that I managed to find out:
- my previous statement that data on existence of goods (from the csv file) increase several times was not true. If for example at the moment the quantity of some goods is shown "75", after import from csv, in which quantity of the same goods equally "1". Existence of these goods increases on "1" and it turns out equal "76" (75+1) if to specify quantity of these goods in the csv file for example "10", after import existence will equal "85" (75+10). I will be extremely grateful if you are able to help me to solve this problem. I would like that existence of goods after all was updated when importing.