"Rome was not built in a day" - a common phrase to describe that if you want to accomplish something, you need to KEEP learning.
For example, if you want to be a professional baseball player, you may need to keep very hard training for certain time.
Learning English also needs to keep training to be good enough.
Some people consider the improvement is as below.
Or some may say like this.
Based on my experience, unfortunately, both of them are wrong.
The truth is like this.
The skill development is step-by-step like a stairway. By keep learning, suddenly you can do something you couldn't do yesterday.
I expect people with good English skills may agree to my idea.
This is why you need to KEEP learning. You may be disappointed while you are in "status-quo" stage, but don't worry. As long as you keep learning, your English skill will "jump up" suddenly one day.
As "Rome was not built in a day", English skills are not built in a day.