The most appropriate way to check how far you master English is by taking an English test. You can take a look at britishlifeskills.com to find out what tests should be passed britishlifeskills.com. Especially when you apply for a resident visa in the UK. They will specify a certain level to pass the visa application. This is so that you can adapt well to the UK environment.
English has other benefits in everyday life and you will not disappointed by learning it. English is a language of instruction that is often used throughout the world both as an introduction to education and everyday communication. At a time when people of various nations gather together in general use English as communication.
Mastering a foreign language allows us to understand every cultural difference and order in every nation. Understanding makes us always be careful and capable in speaking so that people around us feel comfortable about our existence.