Good day,
I am a fellow African developer and would be happy to collaborate across the continent. I am a developer with 10 years of experience developing Django applications. I am confidently able to offer myself as a suitable backend developer. I further have some resources available to me, but it is unclear if your budget refers to the total budget (frontend + backend) or backend only. I am able to offer a simple bootstrap based UI, if required.
I would need to understand your requirements better before I could commit to a timeline and milestones. I would be happy to sign an NDA to access any requirements, scope of work, architecture and other documentation you have as you seem to have a clear understanding of your requirements.
Let's set up a call and a chat, perhaps you could show me the code and we can talk about the way forward. It would be useful to understand the challenges you had with previous developer and the expectations that were set, so that we can properly evaluate your needs for the project.
For example, with the multiple data sources you mentioned (Postgres, Mysql, Excel & Google Sheets), what is the state of these integrations? Is an ETL pipeline required? What level of security of the data is required (encryption at rest?).
These types of requirements are often captured and presented by competent developers to serious clients. I'd be happy to assist; let's discuss further.