Variable products from XML Child Elements

Hello,
I am having a difficulty with importing variable products from my Child XML Elements. Their structure looks like below but when I try to pass the value to the field only one of the sizes and quantities are created as variations. Can you please help me out?

<product_instance id=”21587-1″>
<color id=”1″>ΜΑΡΕΝ</color>
<images>
<image>
https://www.energiers.gr/photos/16-221201-7_001-01.jpg
</image>
</images>
<sizes>
<size id=”21587-x-11″>
<size_name>8 y</size_name>
<size_stock>53</size_stock>
</size>
<size id=”21587-x-13″>
<size_name>10 y</size_name>
<size_stock>49</size_stock>
</size>
<size id=”21587-x-15″>
<size_name>12 y</size_name>
<size_stock>45</size_stock>
</size>
<size id=”21587-x-17″>
<size_name>14 y</size_name>
<size_stock>56</size_stock>
</size>
<size id=”21587-x-19″>
<size_name>16 y</size_name>
<size_stock>33</size_stock>
</size>
<size id=”21587-x-9″>
<size_name>6 y</size_name>
<size_stock>38</size_stock>
</size>
</sizes>
</product_instance>