There are hundreds of websites you can use to study in your free time. Here are 5 that I like:
1) BBC LEARNING ENGLISH https://www.bbc.co.uk/learningenglish/
I really like this website. There is a lot on here that you can do. You can study a number of lessons at each level, so the material is right for you. There are lots of videos and lots of good listening activities (as you would expect from the BBC). 6-minute English is probably the most popular part. You listen to a text for six minutes based on a grammar point or vocabulary point you are interested in. After you listen, you answer some questions based on what you have heard. They provide the audio script so you can check anything you didn’t understand and the important words are explained.
2) THE BRITISH COUNCIL https://www.britishcouncil.org/english
Like on the BBC, there is a lot to do on this website. Most of the activities are specific to your level of English, mostly from A2 to B2, which covers most students. The website is well organised and you can easily find the skill, grammar or vocabulary that you want to practise. The vocabulary lessons are particularly good with nice images of the words that you are learning and plenty of practice to help you remember the words you have learnt. It is always a good idea to keep a record of the words you study in a notebook.
3) CAMBRIDGE ENGLISH ONLINE
The pronunciation exercises are very useful on this website but it can be harder to find what you want than with the BBC or the British Council.
For the pronunciation games go to http://cambridgeenglishonline.com/Phonetics_Focus/
and you can have a lot of fun becoming familiar with all the sounds of English. English spelling is very strange so it is important to learn not just the spelling of English but also the different sounds (phonemes). My favourite game is Shoot-a-Symbol.
4) CAMBRIDGE EXAM PREPARATION (Flo-joe.co.uk)
If you are doing the Advanced, First or Proficiency exam then this is a great website for you. There is a lot of information about each exam and lots of exam practice. The most useful part is the tips section for each part of the test. Each exam is broken down into the individual sections and the website explains what is tested in each part. It tells you what language is focused on, it explains the key language and then it tests you in the same way you are tested in the exam. It is particularly good for preparation at the beginning and end of a Cambridge course.
5) IELTS PREPARATION https://www.ieltsbuddy.com/
If you are planning to do the IELTS exam then this is the website for you. This is quite a technical exam and the different parts of the test are explained well here. Most students find the writing and reading difficult in IELTS. This website is really effective for IELTS writing. There are several lessons explaining how to do the different types of tasks and the most useful aspect is the example answers. Many students find it hard to come up with ideas when writing essays and the example essays give you most of the ideas you will need in the exam.