Take partially built Opencart site and transfer to new theme and take to completed store

I have an existing OpenCart website which was never fully finished. I wish to start again with a fresh install of OpenCart and a new theme. The look and colour scheme of the new theme should be a close proximation of the existing site with logos and menus looking and working similarly. The idea is to take what works from the existing site and use this as a foundation for a new clean build site. There are two extensions from suppliers for the catalog and automatic ordering which need installing. these are supplied as is the new theme. We have a category multi parent module, an import export module, a shuffle products module which also need installed. There are information pages such as delivery information, about us, terms and conditions, contact us, returns, order history, privacy policy which need their content replicated on the new site. The site must be optimise, for speed, usability, and security. Additional functionality above what is in the existing site is.... Features • Speed is too slow and it seems to slow over time. • Enable and set up “PayPal Payments Standard” extension so users can pay using PayPal. Simplify this so not too many entry fields. • Set up Shipping options/costs using Royal Mail built in Opencart option ◦ Set up free UK delivery excluding some counties. ◦ Sales over £20 trigger free shipping. • Add option for “Accept cookies + GDPR”. Advise on what we should use, for things such as analytics. • Add FAQs and information pages such as guides. • Fix the following errors – Warning:unlink(/var/sites/e/[login to view URL] cache/cache.catalog.language.1553477415): No such file or directory in /var/sites/ e/[login to view URL] on line 68 Warning: Division by zero in /var/sites/e/[login to view URL] on line 141 • Checkout more organised and split into simple steps. • Footer Section doesn’t look good, needs improved o Remove the logo o Center the social media icons. Maybe? • In the product page make content block relevant to what is on page. • • Need to gather product reviews from customers who have bought products • Set up a “Featured manufacturers” carousel on the home page. • Install “Product Slider Carousel” on home page for featured categories of product • On the home page set up and add “New products” carousel which will display latest products. • On the product page set up and add a “Featured products” carousel which will display featured products or users also bought kind of related item • On product pages Offer “Buy together” or related products option for lubes, batteries, cleaners etc where required. Various CMS blocks need configuring for information on product pages. • Maybe a text banner for news items on home page? At the end of this process the site must be able to go live and function as a fully fledged store. Documentation must also be supplied as to how the site is constructed and works. This is to allow for easy trouble free administration in the future. After this the site needs to secure, and optimised for SEO etc. There will be on going work.