Building an interactive app where users can ask questions and get answers from others requires a solid approach to both front-end and back-end development, ensuring smooth user interaction and real-time updates. Here are some of the best and fastest ways to create such an app:

1. Use a Pre-built Framework
Bubble: A no-code platform that allows you to quickly build web apps with dynamic content like a Q&A system. Great for prototyping or MVPs.

Adalo: Another no-code platform for building interactive apps, with built-in database support.

OutSystems: A low-code platform for enterprise-grade apps, which might be useful if you want to scale quickly.

2. Choose a Technology Stack (For Custom Development)
Frontend:
React.js or Vue.js for creating a dynamic, responsive user interface.
Use TailwindCSS or Material-UI for a fast and aesthetically pleasing design.

Backend:
Node.js with Express.js for handling real-time requests and data processing. It's fast, scalable, and well-suited for interactive features.
Django (Python) or Ruby on Rails for rapid development and built-in support for user management.

Real-time Communication:
Socket.io (for Node.js) or WebSockets for real-time chat, Q&A, and notifications.
Firebase (NoSQL database) can handle authentication, real-time updates, and notifications without complex server management.

3. Key Features for Interactivity
Question Submission: Allow users to submit questions with rich-text formatting.
Answering: Users can post answers, and these answers can be upvoted or downvoted.
Real-time Interaction: Use WebSockets for immediate answers, notifications, and interactions.
Search and Filters: Enable users to search questions by topics or keywords.
User Profile: Profiles to track users' contributions (questions, answers, upvotes/downvotes).
Moderation and Reporting: Flagging inappropriate content, admins reviewing reports.

4. Tools to Speed Up Development
Firebase: Handles user authentication, real-time database, and hosting. You can create your app without having to manage servers or databases.
Supabase: Open-source alternative to Firebase, offering authentication, database, and storage in a simpler, more customizable form.
Auth0: Quick way to implement authentication with social login, SSO, and more.

5. Database Selection
MongoDB: A document-based database, which works well for flexible data like user-generated content (questions/answers).
PostgreSQL: A relational database for structured data, useful if you need complex queries for things like votes, rankings, etc.
Firebase Firestore: A real-time database, great for apps with dynamic content updates.

6. Speeding Up UI/UX Development
Figma or Sketch for rapid prototyping of the UI.
Storybook.js for component libraries, which help you create reusable interactive components.
Framer Motion (for React) for smooth animations and transitions to make the app feel dynamic.

7. Scalability
Serverless Architecture: Services like AWS Lambda or Google Cloud Functions can scale automatically based on demand.
Docker and Kubernetes can help with managing app deployment and scaling if you need more control over infrastructure.

8. Monetization Options (if relevant)
Premium Content: Users pay to ask questions or access special content.
Advertising: Display ads or sponsored content to generate revenue.
Donations/Subscriptions: Allow users to contribute financially for premium features or content.

9. Testing and Launch
Use Jest (for React) or Mocha (for Node.js) to test components and logic.
Use TestFlight for iOS or Google Play Console for Android to test the app with real users before full launch.
Fast Implementation Example (Using Firebase + React)
Frontend: React for UI, React Router for navigation, and Material-UI for pre-made components.
Backend: Firebase for authentication and Firestore as the database for storing questions, answers, and user data.

Real-time: Firebase Realtime Database or Firestore to update Q&A in real-time.

Authentication: Firebase Auth for quick email/password login or social logins (Google, Facebook).

By using Firebase, you don’t need to worry about server management, and you can focus on building the interactive features.