How long does it take to build a mobile app?

The duration depends less on technology and more on how many decisions you made before starting. With the screens settled, the first version takes days; without them, it gets rewritten three times.

Short answer

The first usable version on a no-code platform: 2–5 days of actual work.
Testing with real users and applying the fixes: roughly one week.
App Store and Google Play review: usually 1–3 days for the first submission.
An agency-built app usually takes between three and six months.

What actually consumes the time

Postponed decisions: which screens exist and what each button does.
The content: copy, images and real data take longer to gather than expected.
Developer accounts: company verification with Apple can take a few days.

A realistic two-week schedule

Days 1–2: settle the screens and the data structure.
Days 3–5: build the screens and add real data.
Days 6–8: test with 5 users and fix whatever blocked them.
Days 9–10: prepare the store assets and submit.

Mistakes that stretch the timeline

Starting the developer accounts on submission day instead of at the beginning.
Adding new features while you are testing.
Waiting for final content before starting to build.

How 4myapp helps

In 4myapp you can publish a PWA version on day one and hand it to testers by link, in parallel with opening the developer accounts. By the time the native builds are ready, the app is already tested — you do not lose weeks waiting serially for things you can do in parallel.