Hi @RudakovaS
In order to create custom properties, you can follow this guide on setting up properties. There is an option to create properties via API as well.
To pass data from your database into the HubSpot portal, you can use Webhooks with workflows.
To set up API keys in HubSpot, you will need to create a Private App.
You can also use the CRM API for Contacts to update contact records.
Hope this helps!