Three wheel bicyle

Oh, I don't think you can find an adult 3-wheels bicycle in Hoi An. You can have it custom made with a fee I think. Ask a mechanic for exact cost. But I think you should ask someone to teach you.

Too bad you live in Hoi An. If you live in Saigon I can teach you. It's super easy.

Thanks Ngan but i am 60 years old and dont have the confidence

As Ngân Khánh sughests above at #2, you'll have to have a three wheeler made up as a special job. Go to a reputable bike shop and ask. Stipulate: overall dimensions and seat hight; wheel sizes front and back.; whether you want a single rear sprocket (fixie) or what gears you do want; if you want baskets under the seat/on the handle bars; if you want breaks on both back wheels as well as the front. Remember that the larger the wheels are, the more comfortable the ride will be. Inflatable tyres are more comfortable than solid tyres; bell that works.
Good luck.

@Oscar39: with a good teacher that won't let you fall and some empty places, you're good to go. Having a bike custom made can cost a small fortune. But you know what suits you best

@Ralph Nha Trang: wow, you can put tones on my name correctly. Your Vietnamese skill is very impressive! 

Any one living in Hoian buy clothing and footwear on line what is a good site and reliable