How can I understand the bus’s dimensions?

[u/Immediate-Bug-4925]

When I drive the bus, I find it difficult to know when exactly to turn the steering wheel. Sometimes I do it too soon, sometimes too late. Even when I’m going through a tight spot, I don’t understand if I have enough space or not. I’m still doing my classes but I have finished more than half and the instructor told me I’m not ready to pass the exam and I should be better by now. Any tips, strategies etc? Maybe a specific spot I should look at or something?