The headgear is adjusted once using the pattern of the old mask. After that, no more changes are made to the top strap ("crown strap") or to the upper straps unless I say so.
Even for washing, the Velcro fasteners are not touched! The straps can be removed from their anchors without having to open the Velcro fasteners.
The nose rests on top of the mask cushion.
When changing masks and connecting the inhaler, make sure that the tubing is white but the connector itself is transparent. You would not be the first caregiver to break the tube irreparably. When it happened, I was lucky to be able to breathe without a mask for a few minutes both times. Today, such a mistake would be fatal.