What would be the best strategy to apply in my scenario?

I have to develop a new version of a software for my company. However, they want me to run the legacy version of the software while the new one is running. This implies that I must use the same database behind the scenes.

The issue is that the database is a Ms Access located in an extremely old Windows server virtual machine. The schema of the DB is also really dirty, as it was made by a non tech guy.

It would be a nighmare performance wise to still use the old DB. But if I change the old DB, the legacy software cannot run.

Also, the server on which the new software will be deployed is Linux based (in a Django web server). I don't think it is easy to run an app served on Linux while its DB is stored in a extremly old Windows VM.

How should I handle the old database while the old and new software run in parallel?