I have assumed the north and south directions, but it would be handy if you clarified these directions on your sketch.

if you post the whole floor plan we could see adjoining rooms and all the doors and windows and do you intend to use the whole dining and lounge for the study with small sofa, piano and Ikea shelf?..do you need a desk and/or other furniture ..what will you use the rooms for and will it need to be shared with other people and purposes eg will it be a separate study/work space from the rest of the house or will you still need to include a dining table, lounges and TV etc

Are you aware you’ve posted on the Australian site? You can change countries in settings. Although you’ll still get some good advice here but first you need to tell us what problem are you trying to resolve. And what functionality are you missing?

there is no point in our suggestions unless your draftee is prepared to either do what you want or explain why it can't be done ..with such limited space there needs to be compromises and imo the original stairs are much too wide and there should be a landing instead of the unsafe uncomfortable winding stairs and there is too much space used in hallways and oversized linen cupboards when the bathroom vanities would have plenty of storage for linen and there's also the understair space with generous extra storage accessed from both the hallway and the laundry. (swopping sides and moving the laundry tub allows a setdown and hanging space when coming in from the garage as well as easier access to more of the understairs)..the new door between bed 4 and ens allows for a bigger shower and helps control privacy and adding furniture shows space for a small dining and family areas and there's a bigger kitchen and more useable pantry storage...upstairs both the ens and bathroom have more standing space and there's a separate vanity and powder room