Have you ever wondered what would be that one question you could ask a prospective language coach that would show you that this person is exactly who you are looking for? Well if you have, or you think such a question would be useful, I am going to tell you it here.
The reality is that at more advanced levels of English, what you need from your English language coach is not just more English. If that is all you are getting, expect your learning to take a LONG time. You, in fact, I suggest need someone who can do far more than that. So let's quickly look at what else you need and why. Once you understand that, then I believe the question you need to ask will become more clear.
I would like to make a few key observations here about what you need understand about learning English.
We have to learn by ourselves
The first key one is that there is a big difference between formal learning, of the kind we do in most classes, with text books or in online courses and what we do when we learn as we are using the language. Let's call that informal learning.
With formal learning, we are being led towards something that someone else decides we need to learn. With informal learning, we decide what we learn and we do it usually without the help of anyone else.
You may be surprised to know that once we are close to native like, most of the language we learned through informal means. Of course there are many things that can be learned formally. However, there are literally millions of things in a language we have to learn by ourselves before we can master it. These things can relate to, for example, finer uses of the language, like conveying subtleties of meaning. These are conveyed by tone, by inflexions, by pauses, by facial expressions, by turn of phrase and so on. A native speaker can say the same thing in MANY ways. To get to that level, we have to master the language. Mastery requires us to learn much about the nature and character of the English language. Not really possible to do that in a formal way.
Formal instruction or learning can only get us so far. The reason why so many people get stuck at a certain level of language, is that they don't quite know what to do to move on. They do not really know what to be effective at informal learning. Many people never fully master this learning process, even though they may get to a good level of language.
How we have been learning may have limitations
What we have been doing has not got us to where we want to get to. It has got us so far. If we are stuck, that means that the the way we are learning is possibly not able to get us further. If that is the case, then no matter how hard we apply ourselves, we will not be able to get any further.
This realisation can be a big step sometimes, one that some people are reluctant to make as they can't understand why what has worked in the past up to now may not work past a point.
One way to understand that would be to consider learning to drive a car. An instructor can help you only so far. After a certain point, usually when you have got your licence, they will stop teaching you. From then on, it's up to you to learn everything else. Until you learn all "those" things you will feel like a novice and other drivers will know you are, by the way you drive.
There are of course some drivers that don't learn much more. But most end up being competent drivers. Learning a language is of course more complex, but the parallels are there.
There may be obstacles preventing us moving on
There may well be obstacles, visible or not, that may be preventing us continuing. Visible ones can sometimes be difficult enough to get around. The invisible ones are a whole different matter. Sometimes over time they may become visible. Other times, we need someone else to bring our attention to them so we can see them for ourselves.
Obstacles can come in different forms, from our own attitudes that are getting in the way, to certain muscular and behavioural patterns that need to become a little more compliant. That has nothing to do with giving up who we are. It is to do with expanding ourselves so we can be more than what we were before.
A skilled coach is someone who is aware of these issues and will be able to answer a question like, "What do I need to do to improve the way I learn?" or "How can you help me become a more skilled learner?.
His/her answer could cover many areas, however in them you would expect to hear something about the 3 areas I touched on above. If they don't talk about any of these areas, My suggestion, if you agree with my analysis above, would be to keep looking!