I want remodel bathroom- what do I need to do?

Call a contractor. Without significant DIY experience, too many things can go wrong. Flip through magazines and peruse the Internet so you know what you want. Show all the contractors the same ideas so you receive comparable bids. Interview at least 3 (or more) licensed contractors. I would also install grab bars and have a seat in the shower for safety. Must be built to local building codes. Here is how to hire a contractor.

https://www.consumer.ftc.gov/articles/0242-hiring-contractor

You need ADA (Americans with Disabilities Act) equipment: comfort height toilet (elongated bowl is more comfortable, if you have the space) with grab bars at side and rear of toilet; walk in shower with sloping drain, or low threshold shower, both with wall mounted grab bars at side, rear, front of shower. If she uses wheelchair, bathroom must provide 5' radius in which to turn chair (same for shower, if needed). Insure the door is easily opened from outside and inside, in case of falls (so she does not block door from being opened). Bench or large seat in shower is helpful, along with a hand held shower head with a vertical bar and " dock " to permit hands free showering for a seated person, if so desired. Plan to place the soap and shampoo in easily accessible positions (no liquid soaps that pose a slip and fall hazard). Flooring should have smaller tiles with many grout lines for added security when standing. Round grab bars are easier to grab in case of falls. They should be mounted into wall studs, and be caoable of supporting 250# of force. Bars must be installed for her height. Make sure one is placed at a position she can reach if she falls. Put in an overhead light, safe for shower area. Maximize lighting by placing lights on either side of mirror, one above mirror, and very good exhaust fan with auto sensor for humidity. Use adequate wattage in lights, considering her age and vision, but no bare bulbs or clear shades, due to glare.

Yes thank you