Software quality depends on many factors such as: Functionality, usability, performance, reliability, portability, interoperability, scalability, and reusability (see full description here).
There are many aspects that contribute to a good design and to the quality of your software. It is important to follow the best practices and think about the design of your software. Luckily, many experienced programmers have developed best practices over a substantial period of time. These best practices can help inexperienced developers to learn software design easily and quickly.
The first thing you can learn that will immediately improve the quality of software is to follow the SOLID Principles of Software Design. Following those 5 principles will result in a more understandable, flexible and maintainable code. You can read more here:
Design Patterns are well-thought-of, reusable solutions to common recurring problems that developers face during software development. They are considered a common terminology between experienced developers. Design Patterns are general and can be applied to any programming language. The following are some references to get you started.
Object Oriented Programming (OOP):
Object Oriented Programming (OOP) is a method of structuring functions and data into objects that can help organize software projects. It has a number of advantages, including improving reusability and maintainability. It is highly encouraged to use OOP in large-scale projects