How to migrate to a new architecture while isolating old code?

Question

Refactoring

There is a project on Laravel with a "smelling" code base and a crooked implementation of a modular architecture, the same crooked implementation of repositories and a terrible hodgepodge in models.
We urgently need to save it, while rolling into a normal architecture.

Actually, what are the methods of architecture refactoring/migration?
Are there any books on the subject?

Answer 1

Read Refactoring by Martin Fowler

Answer 2

https://refactoring.guru/en/refactoring/techniques
Maybe something will help here.

Answer 3

If the infrastructure allows, then you can create a new project, write the old functionality in it in a normal way and separate the urls at the server level that will look at the new and old code base. Well, the standard way is to cover everything with tests and refactor a little...