Bug fixes and refinement of a complex project on Bitrix

Good afternoon.

We are looking for a professional developer on 1C-Bitrix to finalize a complex project. The project is a marketplace with a personal account of the supplier and the buyer. Sale, purchase is possible as part of the usual process, the choice of goods - basket - payment. So it is in the framework of the auction.
We are ready to provide the terms of reference for the analysis after the initial communication.
Please write your suggestions with a description of the cost of your work. Monthly or hourly. So that there is an opportunity to start from something when evaluating