Required Prestashop Expert to Resolve My Website Issue

[login to view URL] we enable guest checkout in the BO Preferences and any client on our site want to buy with registering but purchase as a guest , they cannot proceed, because they get this strange error (An error occurred while creating your account.) while I debug I found that the $custome model is not adding in the customer group because its let client get new customer id. 2. Adding extra service features such as add additional services to the product, add related product accessories. [login to view URL] whole shop need customizing to fit our service and desire. 4. Interrogation of main header services with presathop as i have explained above. Second just let you know for more info to check w3(dot)cnss(dot)se to see and understand that's my prestashop is not a nonstandard webshop as a normal site. Its integrated with main index header developed in php. The two must work together as we you are going to create 1 data base for services and products. We provide clients products that are connected to same kind of service, and this is where must of your challenge will be to see your expertise. so your tasks are as i described in the ad. 1. Fix the payment and registration bug, so that clients can continue there purchase. And fixing errors all errors permanently and properly. 2. Customizing the shopping cart and purchase process for a better clients experiences. ( point 1 and 2 are the same ) 3. Add additional plugins for services and accessories, for example when you buy a service or product you can add service or related accessories from shop or main header. ( with main header mean [login to view URL] php, where you see solutions or under products and the i pad. The information is dynamic and get it from prestashop. so the main header and prestashop work already smoothly, but this process has some kind of time delay when connecting from [login to view URL] php home to prestashop, and also the clinking speed is very slow in both ways. 4. Customize and fixing the prestashop design and functions, That includes banners, search functions and proper orienteering and organised webshop including its functions of the shop as intended from the begging. Fotter header should have same design and front index [login to view URL] php. 5. Arrange categories and catalog,missing links errors or page not found, add top seller, hot products, special category and highlight them.