Import invoices with several items into InvoiceNinja

i am still trying to import our old assets into InvoiceNinja. The exported .csv contains an several rows per line of the actual invoice table: invoice/lines/0/id | invoice/lines/0/position | invoice/lines/0/quantity | invoice/lines/0/description | invoice/lines/0/tax | invoice/lines/0/tax_amount | invoice/lines/0/product_id | invoice/lines/0/price | invoice/lines/0/units | invoice/lines/0/total | invoice/lines/1/id | invoice/lines/1/position | invoice/lines/1/quantity | invoice/lines/1/description | invoice/lines/1/tax | invoice/lines/1/tax_amount | invoice/lines/1/product_id | invoice/lines/1/price | invoice/lines/1/units | invoice/lines/1/total | invoice/due_date | invoice/paid_date -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- and so on. Any idea how to import the content properly into invoiceninja? is it fact that invoiceninja uses every item of an invoice as an own invoice and just aggregates them below …