Project management with details

We need every step of the project to be identified with its duration and estimated cost as follow :

The project is an online store that has a warehouse, dispatch area where goods are sorted and packaged for cusomers, and a delivery service.

The online store will be allowing sellers to store their items in the warehouse and will enlist them in the website. 

A system should be established to link the seller with the online store. Also, the system should be enterprise to keep track on the stock items and the revenues generated. 

The project is to be executed and completed in 16 months.

Based on this information, a gantt chart, critical path, and calculations will be don

Details each step is important

no palgiarism

Project management backgroud preferred