Build stairs through a wooden beam ceiling

Hello,

I am currently planning our house renovation. The house is to be vertically divided so that two independent apartments over two floors each will be created. Apartment 1 already has a staircase from the ground floor to the upper floor; for apartment 2, a new staircase needs to be planned. The room height is 240 cm and the ceilings consist of wooden beams. As far as I know, it should basically be possible to make a ceiling opening for a staircase. However, I am overwhelmed with planning the staircase layout: the apartment will be occupied by my father in the future, meaning the staircase should be as little winding as possible, partly for safety reasons, partly so that a potential stairlift would be cheaper. Ideally, a straight staircase or a staircase with a landing, or also with a slight winding/landing at the entrance/exit.

The plan is a first draft; room 2 and the bathroom may still be made smaller, doors may be moved, etc… The separated hallway is not a must either; the wall could be removed.

The entrance marked in red should ideally not be blocked by the staircase (the door will be locked but reopened for care if needed). The WC on the ground floor is only feasible at this location.

Are there possibly any solution ideas? I would be very grateful :)

Thank you.
Best regards,
Ev

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However, I am overwhelmed with planning the staircase layout:

You are not alone in that. You can see far too little here. Show the entire house - both apartments, old/new floor plans, and also a section from which the beam structure can be seen. Also consider: a) that extensive remodeling can jeopardize the existing building protection, and b) the fire protection between the residential units.