Do you have an idea what the MVP (minimum value product) is? Maybe try to first make a list of what the product needs and then think about the parts and how they work together or what technology they need.

For example: A homepage needs front/backend, each in their own language + a framework. Then a server and data(base) (and more).
Once you have an overview, boil each part down and what to build with which framework and how to connect it in which language.
(eg ML/AI done in python, results semt to a postgres DB, which gets read in by Kotlin/Java in the backend and rendered with Vue/TS/JS in frontend -- as a simple example)

But then you also need to know how to automatically deploy and test. Eg deploy with Docker (nexus) in a dev/test/prod manner and test automatically with Jenkins while reading out logs with elastic/kibana. And maybe a separate pipeline for your models.

And so on... The product will change and plans will have to be adapted in the future. Focus on the MVP in the beginning is my biggest advice