How to do behavioural analysis on a smartphone?

Question

I need to track social media usage patterns, and engagement sentiment of the individual to monitor the person's behaviour and give a mental health score based on the data analysed. There is one constraint : It should be on-device , i.e, no cloud APIs.

It is part of a mental health monitoring system project, where I collect data from various sources and analyse their mental health real time, on-device.

I need to implement 3 different models -

1. Text Input Analysis
2. Audio Analysis
3. Search History and Behavioural Analysis

I haven't done a lot of ML projects, and this is the first where I am completely doing it alone. So I do not know where to start from and what to do.