Hi Iwata ,
Make sure you have only one thread for queues.
you can disallow concurrent execution on microflows. This will paralel execution in the batch process.
This concurrent execution setting can you find in the settings of a microflow.
For screens, it's harder.
You can maybe add an identifier to a session on which screen a user is.
And before entering a given screen, you can check if there is no other session currently on that screen.
Hope this helps,