Estimations and reflections

Recently I was thinking about improving my English communication skills. Maybe, I don't know enough of words?
I searched for a most frequently used English words (google 5000 common English words), and found the list.
I looked through it, and I think I know more than 95% of the words. I've made a couple of trials - like knowledge test on randomly selected sample of 100 words, and again, I've found that I know >95% of the words from any random sample.
OK, I suppose my dictionary is not that bad, 5000 words is definitely sufficient for any meaningful conversation, isn't it?

But when I speak, I'm using just a small subset of what I know. It's like having two (or even three) separate memories - one for reading, another (tightly connected with the first) for listening, and one more for speaking (and maybe writing).
Well, what's next? Maybe, I'll try to use the words from my dictionary in a more active way. For example, I can select randomly 30 (or 50) words and use them in a conversation session or for writing an essay?
Any hints from professional teachers?

I do not find memorizing vocabulary in isolation overly effective.I would recommend you consider developing your vocabulary skills in context. By 'in context', I mean that vocabulary and tasks should be linked together.
What seems to well for me, and my students, is selecting a task (such as writing a news report, describing how something works, etc...) and doing it over and over, editing and upgrading vocabulary in the process.

For instance, you could paraphrase a news article:
Apples' sales surged this year, reaching their highest level in five years.

Over the past year, Apple saw its highest sales in five years, sales which drastically outpaced previous years.

Apples' sales increased drammatically this fiscal year. Compared to the past five years, Apples' sales during all four quarters were unprecedented. 

Creating exercises such as this allows you reflect on your word choices in specific contexts. You can try and write 5 or 6 versions of the same paper, or practice paraphrasing other people's writings. One useful thing about this exercise, is you can practice changing how formal your writing is; at times, you can try to write as complex as you can; at other times, try expressing the ideas in as simple language as possible.

Estimations and reflections

Recently I was thinking about improving my English communication skills. Maybe I don't know enough of words?

I searched for the most frequently used English words (google 5000 common English words), and found the list.

I looked through it, and I think I know more than 95% of the words. I've made a couple of trials - like knowledge test on randomly selected sample of 100 words, and again, I've found that I know >95% of the words from any random sample.

OK, I suppose my dictionary is not that bad, 5000 words is definitely sufficient for any meaningful conversation, isn't it?

But when I speak, I'm using just a small subset of what I know. It's like having two (or even three) separate memories - one for reading, another (tightly connected with the first) for listening, and one more for speaking (and maybe writing).

Well, what's next? Maybe I'll try to use the words from my dictionary in a more active way. For example, I can select randomly 30 (or 50) words and use them in a conversation session or for writing an essay?
Any hints from professional teachers?

A big vocabulary is great, and you write well, but I suspect you might just need to work with idioma and phrasal verbs, and responding to someone else. The next time you take a class, ask your teacher to give you some common British or American expressions.