Configuration

Dear all, 

I have two problems and am quite under pressure, since my online seminar runs next Sat & Sun.

1. I have prepared different whiteboards and would like to have them edited and saved in several breakout rooms.

However, my participants do not have access to these whiteboards.

What setting do I have to make so that each group of breakout rooms can open, edit and save their own whiteboard (my own)?

I can open a template myself from the breakout room, but as soon as I leave the room it is closed.

Is there a trick to access prepared whiteboards from the breakout room? I am offered whiteboard, but then only a white sheet appears....

2. Problem: screen sharing. How can I access individual applications? At the moment, only the desktop is offered to me, which means that I have to awkwardly "position" individual windows in advance in order to be able to share them.
Does anyone have a workaround or an idea? That would be great.