Drupal 9 replacement site sauna builder

The project is a new drupal 9 site.
for replacement of https://www.saunamania.be/

The client is a builder of saunas on demand and supplier for people who want to build their own sauna.
The goal is to have a modern website respecting current theme but freshen up no specific design available.
Mobile first barrio sass as parent theme.
With modern web shop, No shipment with external transporters, own delivery.
Each order will be sent to specified user to validate the technical compatibility of the parts.
No payment activated but should be easily enabled eg addmollie key or stripe.

Keep current google ranking and improve SEO

multiple languages: dutch, french, english

Basic functionality as current site:
same of current site
information pages, different kinds of saunas
listing of products for sale
web shop with products with variations
products have stock
for example product magnolia wood
variation 1: board 2m
variation 2: board 2,10 m
variation 3: board 2,70 m

no stock of variation x → variation is grayed out or hidden ( to be decided)

product sheet has technical information, pictures, detail pictures the usual
with list(view) of available variations

Faq question contenttype
Faq page ->list/view of faqs

page with promotions (vieuw)

media support
page with list of movies(steps of building a sauna)/course

layout builder if needed
good search for products, instructions

All default site best practices for SEO
Meta tag, path auto

timing is flexible