To speed up your app you can follow below steps:

Combine API Requests:

Discuss with your backend developer to merge the APIs into a single request that returns all the required data in one response, or reduce it from 4 to 2 or something like that. For example, if one API fetches homepage details and another fetches user details, pass user-specific parameters in a single request and get everything at once.

Optimize Frontend Loading:

If combining APIs isn't possible, prioritize loading essential data first. Use shimmer placeholders or similar for sections dependent on secondary APIs. Fetch secondory prioritized data in background using asynchronous updates (e.g., StreamBuilder or FutureBuilder).

Caching:

Cache static or semi-static data to reduce repeated API calls.

UI Optimization:

Simplify widget trees for complex designs and avoid unnecessary rebuilds