Switch between activities of the same package

Hi, guys. I have an application which has Android auto build in features. If I am not mistaking all the functionality of an android auto is running in a separate activity besides from the Main activity. My question is how to change focus from the main activity to the activity related to projection of android auto. Using start activity command is NOT an option, because it is already started and running in parallel with the Main. I need to get the excess to a native part of the android auto in order to interact with it. I only have access to the web view part, because the app is hybrid. In Native I can only see the contex of the phone, not the projection.