One of the reasons why English is a very candidate for an international second language. Interestingly, most of its speakers are second-language speakers. If we count only first-language speakers, the Romance languages (taken together) are in the second place after Chinese (which is not at all as monolithic as people think); the list of language families by percentage of speakers in mankind is also very outspoken in this respect.
The main flaw of English as an international second language is that if you hear a word, you never know how to write it, and if you read an unknown word, you don’t know how it is pronounced. If you want to test your knowledge of English pronunciation, try to read the poem The Chaos aloud. It is long but worthwhile, because it gets more and more absurd. Even for English native speakers Gerald Nolst Trenité’s poem is quite a task, and possibly an eye-opener. You can even test automatic reading of this text. Have fun and better use Esperanto as a second language for communicating with your friends abroad.