I cannot seem to nest navigators in a proper way - react-native

Question

i'm developing an app in react-native, using react-navigation. I really love this library and the flexibility of it, but for the love of me i cannot seem to nest the navigators according to the schema i have.
The schema is actually not that complicated, so i'll try to explain it with words as well with a little schema.
My app will have a splash screen during which i'll do some logic (initialize the store, etc. etc.). The next screen is based on this logic, and can lead to a tutorial screen or the home itself.
Once the user has completed the tutorial it will be navigated to the home screen.
The user shouldn't be able to back to the tutorial from the home screen, should he come from there.
In the home screen i want a drawer navigator, that can lead to N screens . Each of this screen should just have a title and the back button, that brings back to the home.
One of this screen is the tutorial itself, which should have the same behaviour as the first time.
So to sum up:
Splash;
Tutorial (optional)
Home
Screen1;
Screen2;
....
Tutorial.
This is the code of my navigator:
import { createStackNavigator, createAppContainer, createDrawerNavigator, createSwitchNavigator } from 'react-navigation';
import HomeScreen from './home';
import Details from './details';
import SplashScreen from './splash';
import Tutorial from './tutorial';
const TutorialStack = createStackNavigator(
{ Tutorial },
{
mode: 'modal',
headerMode: 'none'
}
);
const DrawerNavigator = createDrawerNavigator(
{
Tutorial,
SplashScreen,
Home: HomeScreen,
Details
},
{
defaultNavigationOptions: {
drawerLockMode: 'locked-closed'
},
drawerBackgroundColor: 'rgba(255,255,255,.5)',
overlayColor: '#6b52ae',
contentOptions: {
activeTintColor: '#fff',
activeBackgroundColor: '#6b52ae'
}
}
);
const RootStack = createStackNavigator(
{
Home: HomeScreen,
DrawerNavigator
},
{
initialRouteName: 'Home',
defaultNavigationOptions: {
headerStyle: {
backgroundColor: '#f4511e'
},
headerTintColor: '#fff',
headerTitleStyle: {
fontWeight: 'bold'
}
}
},
);
const AppNavigator = createSwitchNavigator({
SplashScreen,
TutorialStack,
RootStack
}, {
mode: 'modal',
headerMode: 'none'
});
const AppContainer = createAppContainer(AppNavigator);
export default AppContainer;
I get the transitions almost correctly, but:
If i try to go back to the tutorial, i can (and i also inherit the header from the next navigator)
I can go back from a screen (e.g. Details) to home, and when i get there i get another 'back' arrow - this way i can go back and forth from home to details indefinetly.
I know i'm doing something wrong with the nesting, but i cannot seem to get it right.
Thanks to anyone who will help me!