Fixing mobile App and website issues and supervise the handover

i have a native e-commerce mobile App (IOS/Android) and a website there are in total 3 Apps (Customer, merchant and driver) and 3 admin panels (Admin, Merchant and delivery) the selected freelancer should be able to rectify the current order flow and troubleshoot the issues to ensure from order placing till delivery there is no issues 2 Resolve the Driver app crashing 3. Resolve guest mode in IOS 4. change the current order structure whereby currently if the customer purchased 3 items from the same shop the system generates 3 different orders (1 order per item ) while it should be 1 item per purchase 5. fix the filter issues currently you cant filter fer price or alphabet only you need to select the category and sub-category which should not be the case 6. add more information on the admin panel such as customer information in the order screen and other information with a maximum of 6 information 7. validate the current app structure and fix any API or invalid logic issue 8. resolve the promo code issue. currently, if the promo code is associated to specific store the promo code will be applied for the entire orders which is not the right logic. 9. finalize the integration with payment gateway 10. assist post-going life for 2 weeks. then we can sign 1 year support contract afterwards 11. ensure merchant can edit/update their products and filter them 12. add validation to the merchant while creating a product to ensure all required fields are added Testflight access will be granted to the developer to review the current build and assess the situation before awarding. Required timeline to resolve should not exceed 3 weeks Backend is PHP Codegnator and Node.JS