android – I want to build and setup my own AI agent using a local storage and my own device. How could I do that?

I’m new in this topic and I want to learn about it. If I want my own chatGPT version working, learning, replying to my requests working isolated way on my own computer or cellphone. What do I need to do step by step to achieve this? Thanks.

All the solutions that I have seen work on remote servers.