@aftechro thank you for writing me in my native language! 🙂 I'll keep an eye on this project and moreover I can help you with some suggestions. My understanding is that this app aims to be a mix of CRM - configure quote - invoicing - ticketing and analytics. I'll start from the CRM which in the flow should be the first development area.
As I suggestion, based on my CRM user experience (Salesforce, Hubspot & other custom made CRM) i would differentiate between prospects and customers. First you have to add the prospect, with all the details you have. After you sign a contract/order form the prospect should change its status and to automatically move within new area of the app - Customers. Practically you take over the metadata you already have (from prospect), and you have to add the rest of it like: contract start date, monthly fee, installation fee, payment term, delivery period, etc. Some of this information can be taken either from quote or has to be manually filled. When you have the customer configured in the system then the prospect should be locked (no activity should be permitted as is already a customer).
There are many other suggestion I have but not sure if you have time to allocate to this project as it requires resources.
Happily to discuss more in a conf call if you want.