Define your Target Audience
Keep in mind that while the laws of your country may restrict you, it is quite another matter if you intend to grow your company internationally right from the start. International licenses and permissions are required depending on where your exchange business will be presented. You will require the assistance of a lawyer with knowledge of international trade law.

Design
This is what the user sees right away after opening the app. Follow current best practices and consider the product's requirements if you want a beautiful and functional design. The following are the steps in the design process. Wireframes are used to implement the most important features of a design in its early stages as a foundation for future design. A thorough visualization of the user's interaction with the application is required to avoid any potential UX-related issues.

Front End Back End Development
When you start getting real working builds, programming becomes more fun. It is much simpler to make improvements if suggestions are made while the project is still being worked on rather than after it has been fully completed. This is the reason you can not skip this process.

1.If you're interested in creating a Bitcoin exchange, there are two groups of programmers involved
2.Old-school app developer
3.Blockchain programmers

API
Application programming interfaces (APIs) are a subset of back-end software that is inaccessible to end users. Internal logic and crucial tasks are performed by the application's code.

1.Identification and authorization checks for users
2.The admin panel's server-side functionality
3.Individual Bitcoin users make bets and conduct transactions.
4.APIs can be utilized by third-party organizations.

For your reference, I suggest you take a look at the Innblockchain Academy blog to learn How to Build a Crypto Trading Platform. Sure, you will get an idea about that.