The area of the strata plan that Tina accurately describes will potentially outline a “stratum” for courtyards. This will be what you need to know to start to understand who is responsible.
The strata plan will also show where your courtyard is and they are usually tied to the lot with a “veniculum”. Looks like an S that has fallen over.
The best place to start looking will be to grab a copy of your strata plan and look for the notes on it and see if they clearly details these things for you.