Hi Sabid,
I think below points are worth considering.
1. Just refresh your grammar concepts. Not from the scratch, but when ever you get stuck or confused with some areas in writing or speaking.
2. Practice writing & Speaking every day
3. Go back and check every day how to write an argument and discussion essay . I mean the structure and flow. For this I suggest you to check Ryan's YouTube channel.
4. For improving vocabulary, spend at-least 2 hours every day in reading 'The Guardian' newspaper or content available on proprietary web-site. Navigate to section A-Z on the site and you'll find variety of topics and subjects. Although every one advice's that read what ever that fascinates, but I recommend you to go through every area i.e. Society, community, politics, money, art, youth, generations, children, family and many more.
5. Try to observe the grammar while reading i.e. what are the adjectives prepositions used with the words that you may confront for the first time.
hmmm... Let everyone know what tips and tricks you might think are vital to improve writing.
Regards,
Bunni