You can go from one entity to the other using the app navigation
Here is an example of a project's screen:
Each screen is made of various modules you can remove or add upon your needs
The example above shows the screen of a project with the modules:
Project details, Subproject, Budget, Tasks, Billing Methods, Budget Status and a Report.
If you have a complex organization with various branches, here is the full picture, with the data model of the entities and how it impacts the way people fill their timesheets.