You must provide an exactly measured floor plan of the existing structure, with marked drainage pipes, downpipe, height information for the ceiling structure (top edge of finished floor - OKRD), information about the ceiling structure (reinforced concrete ceiling with composite screed, wooden beam ceiling, etc.), indication of the max. buildup height of the new top edge of finished floor (clear passage dimension of the door), and indication of fixed points that cannot be changed, etc.
Otherwise, no reasonable answer can be found to your question, except for general advice and opinions that will not help you further. This type of sanitary planning is quite delicate. Every centimeter counts for the buildup height or the necessary slope of the drainage pipes.