I want to develop an instant messaging app from where I can start?

If you want to develop an Instant messaging app then you will start from the stretch like

1. Research Competitors
2. Come up with a unique idea and features
3. Take paper and pencil and create your own design
4. Choose the best technologies to create a website and App.
5. Hire a professional for development & content creator to create the best content
6. Think about website messaging[1]

• What is our product about
• What makes you different
• Have we set the right expectations
• Create a Simple and elegant design

Top Features of Instant messaging app:

• Smooth Cloud-Based File Storage[1]
• Cross-Functional Collaboration
• Internal Messaging
• External Notifications/ Pop-ups
• Calendar different Views
• High Security
• Mobile Responsive Design
• Intuitive Interface
• Perfect workflow

Top 5 Instant messaging app for Startups and Entrepreneurs:

Oneteam[2]

Re-invent team communication and collaboration With A Secure Instant Messaging Apps

Advantages:

• Encrypted, business-only communication within pre-populated contact lists
• Connect with business contacts over VoIP calling
• Read receipts to know if your messages are sent, received and read
• Flag Messages for marking important messages for quick referencing
• Message forwarding to make communication easier
• Large file sharing up to 25 MB each
• Activity/News Feed
• Alerts/Notifications
• Audio/video Calls
• File Sharing
• Real-time Chat
• Mobile Access
• Quick Search