You can learn English at home in the Netherlands, but also in England, Ireland or another English-speaking country. If you are going to learn English in an English-speaking country, the experience is that it goes faster, produces better results and is often a lot more fun. You live in an English-speaking environment, you pick up the culture, you are forced to get by in English, you have English-speaking friends, etc. You must ensure that the conditions in the language school are such that you are assured of results . Many language schools have poor teachers, large classes with only Dutch students, few facilities, mediocre guidance, etc.
English is the most important language in the world!
In international circles (business, international organizations), English is in principle the main language
In many countries, English is the first or second official language (USA, Canada, Australia, New Zealand, South Africa, India, Philippines, Ghana, Nigeria, Malta).