‘come together’ is used to say that different parts of a whole have been successfully combined. It may refer to a plan, a process, a project, a construction, etc. : ‘the project is starting to come together’ ‘get together’ is an informal way of saying ‘meeting’ ; it can be used as a noun : ‘we’re having a get-together next Tuesday, would you like to come ?’ or a verb : ‘let’s all get together and try to sort this out’.

Come together tends to be used in reference to some sort of joint purpose. Get together is more informal and is generally used to describe social situations.

Hey Rodrigo , they are used interchangeably