A Good way to better your English is to travel abroad and find a job. Britain has a very flexible job market, people are often paid by the week and employers are happy to have foreign workers who work hard at a job.
The minimum wage is currently £5.13 (18-20) £6.50 per hour (over 21) but you may have to pay some tax although up to around £10,000 per year may be tax free in the UK and the first few months may also be tax free.
Or you could join a VOLUNTEER PROGRAMME to travel abroad and improve your English and help others. You can do something of value and learn while working with native English speakers all day long.
Be prepared to work hard and you will have an excellent life changing experience.