Solved!If anyone is interested,
i've changed @P_ID and @LANG_ID to int in fnKartrisProducts_GetName and line 20 in spKartrisProducts_GetTopList to
SELECT TOP (@Limit) vKartrisCategoryProductsVersionsLink.P_ID, [dbo].[fnKartrisProducts_GetName](vKartrisCategoryProductsVersionsLink.P_ID, @LANG_ID) AS P_Name