At advanced level (C1) you will probably be able to express a wide range of ideas reasonably effectively but you will still be making quite a number of errors. You will need to reduce your basic errors to a very low level and to push on and start to master more difficult areas of English. As your English gets to advanced level, expert users of English will stop filtering their English so understanding what they are saying and writing will still be an issue.

Have a look at my higher level mini-lessons

Tips:

• Try  to expand your awareness of multiple meanings by checking new words and phrases in context from this website.
• Aim to extend your knowledge of vocabulary while reducing your errors in grammar and pronunciation.
• Try to read a novel (native reader level) that has plenty of dialogue. Detective novels can be very suitable and motivating.
• Keep up with news and current affairs so you add to your vocabulary and have something new to say in conversations. Traditional newspapers can be helpful but tend to be too full of cultural references and vocabulary used in special ways. It’s often better to go to their websites as the articles are more accessible.
• Use exercises from Cambridge English: Advanced to test what you know. Browse the Internet for free exercises.
• Try your best to widen your circle of expert/native users. They will help you get to the next level and understand the cultural aspect of using English eg indirectness.
• Be disciplined to review your ever-growing vocabulary.
• Pay particular attention to collocations and expressions/groups of words.