Migrating to Azure AD and SharePoint from on-premises AD. How to do it right?

Question

SharePoint

Can you please tell me the steps for migrating from a local server to the AzureAD and ShrarePoint platform?

Introductory:

• Local AD server, DNS, File server (with perennial user folders);
  
• Azure AD (manually duplicated all local AD accounts without any synchronization with local AD);
  
• Empty SharePoint (it is planned to transfer user folders there)
  

The organization actively uses Office 365, login with accounts like new-domain.com, all local AD accounts are duplicated (manually).
Local AD is used to access a file server with folders and log on to a domain PC, an account like old-domain.com.

There is no experience of such migration, although it can be solved, but I would like to hear some best practices from more experienced colleagues in advance, so as not to screw up the jambs and not step on the rake that was stepped on by "hundreds who walked before me." :)

Thank you.