develop website core

We need to create a Wordpress-based website. This project relates to developing website core – the communication flow with a client from the moment of placing the order to results delivery. The objective is to create integrated system of plugins and ensure client communication thru website works smoothly both for client and website administrator. The target audience is Russians, therefore we will need to integrate with some local services thru API (SMS, online payments). This is how client communication should look like: 1) The client places an order by completing complex form with conditional logic (gravity forms?). The order is processed by e-commerce plugin (woocommerce?). Client should be able to upload huge files, it can be 1-5-10 or even 20+ gigabytes (integration with filepicker service?). 2) Based on that order we provide services to the client and periodically send notifications for changed order status (woocommerce? or integration with CRM plugin, plus integration with Russian SMS gateways, e.g. [login to view URL] or [login to view URL]). 3) The result of our services is a folder with files, which we prepare for every client. Link to download those files should be available to the client right after he or she pays the invoice. As soon as we have the files (link for download) ready we invoice the client (wp-invoice? woocommerce?) and he or she pays it thru Russian payment gateway (e.g., Robokassa, I found corresponding plugin for woocommerce but not for wp-invoice). If you suggest to use other plugins to solve certain tasks you must be able to explain your choice. Ideally the integration with other plugins (gravity forms, woocommerce, wp-invoice, etc.) should be done in non-distractive way to support upgrading those plugins to new versions without breaking website operations. I will gladly answer your questions. Please estimate project delivery dates, make a high-level outline for project stages and suggest your fixed budget for each project stage (e.g., integration of wp-invoice with local payment gateway will cost us $X, integration of woocommerce with local SMS gateway will cost us $Y). Please refer to any woocommerce and wordpress plugin integration \ development projects. Upon completing this project we will need to work on website design and integrate created system with 1) local shipping company thru API (to calculate shipping costs and place the order for pickup or delivery), 2) extensive user profiles (gravity forms?), 3) CRM. Therefore if your work is completed successfully you will be hired for upcoming projects. Kindly consider it when placing your bid.