If you want to study harder and better then take an English test. It sounds at least strange but it is well known that people study harder and much better if they study for a test.
You may consider the test as being your reason for learning English and more than that you will have one more certificate to add to your curriculum vitae/resume.
Testing may help you answer the question “Do you know what you have learned?” and in many circumstances “How well can you use what you have learned?”
During the test (and before) you will try very hard to remember everything you have learned and that is the best way to cement the knowledge you have accumulated.
My students are teenagers and they learn English with a single purpose in mind and that is to get a good result at speaking test. If there is no test then probably just a small fraction of them will try to learn the lessons.
Tests also help you to build confidence. A good test result doesn’t do anything but to recompense you for your effort of learning and increase your confidence, the confidence that is so important for every learner of English.