You do not need to remodel your home. A few targeted changes make a real difference.
Throughout the home: reduce clutter and background noise, and keep lighting good and even. Shadows and dim corners can frighten a dementia brain, and glare can confuse it. Remove or cover busy patterns and large mirrors if reflections cause distress.
Kitchen and dining: reduce distractions at mealtimes. Use a plate that contrasts with the food, so it stands out and is easier to see. Offer finger foods if utensils have become hard. Keep the table simple.
Bathroom: this is a common site of distress. Warm the room, use contrast (a colored toilet seat against a white floor is easier to find), add grab bars and non slip surfaces, and reduce echo and harsh light where you can.
Bedroom: keep it calm and dim in the evening, with a clear, lit path to the bathroom for night time. Night lights reduce fear and falls.
Pathways and signs: keep a clear path to the rooms used most. Simple labels or pictures on doors and drawers can help your person find what they need and preserve independence.
The principle behind all of it: simplify, add contrast where it helps, and remove what confuses. You are engineering calm into the background so your person has to work less hard to feel safe.