Steps in Database design and implementation

What are the main and necessary steps in the DB design and implementation process?
Let's enumerate and explain them...

1. User requirements. First we need them, we need a user capable of using a computer, understanding our language, etc.
2. Conceptual design. This is used to describe information that the DB will contain. This is where we typically use the ER (Entity - Relationship) model, although some people refer to this design as drawing a simple schema about relationships without using the full version of ER model. 
• Input: Requirement specifications to build the DB
• Output: Conceptual schema
3. Logical design. Used to describe the structure of the DB that can be processed by the DBMS (Database Management System), it can depend on the type of data the DBMS can used but not on the DBMS itself. Here we'll use the ER, including Attributes and Primary, Foreign an Alternative keys.
• Input: Conceptual schema
• Output: Logical schema 
4. Physical design. At this point we create the file index and the design of the filesystem.
5. Implementation. We test the DB.

CONCEPTUAL VS LOGICAL VS PHYSICAL DESIGN

Source: https://www.1keydata.com/datawarehousing/data-modeling-levels.html