delta migration

I have made a copy of my live database and used it for migration. Now I am ready with Magento 2 and wanted to do the deltamigration. That does not work.

I have tried to do the datamigration again and some data get tranfered like customers but orders/invoices etc. and products are not.

Do I have to start all over again? A months work down the drain? Is there a way to migrate my orders again?