Getting information about job changes

I've been browsing REST API documentation (https://docs.rws.com/860026/488114/worldserver-11-7-developer-documentation) and I can't understand the workflow for the following use case:
1) We create job in Worldserver and upload files to be translated

2) When they are translated we need to get the translated files

I have a number of questions:

1) When we create project group we receive projectGroupId back. But I don't see how can I get projects with this projectGroupId without quering all active projects and checking their projectGroupId

2) Is there a way to see that project was updated? Maybe some kind of notification/webhooks. Or do we need to load all projects information on timer? Especially important for redeliveries, when project was completed, but translated files get updated at a later date.

Thank you for your help.