Experienced Adalo developer. I have examples of work I can show you. I currently work on two massive and complex Adalo projects.
Are you planning to use internal Adalo database? This now has external API, brand new feature if you were interested.
I have done connection to Google Sheets, Airtable, Integromat, Zapier, third party APIs.
I didn't do an external database beyond Sheets and Airtable, I assume this would be easy enough though.
I have an Adalo app published on Google Play store, I have not tried iOS yet.
UK Native, good communication. Contact me if interested. I prefer to work hourly via timetracker.