You should do English work.
I have to improve my English ability.
You should persist in your efforts to learn English.
You must endeavor to improve your English.
If you are to improve your English, you had better go to countries where it is spoken.
Whether you may study English literature or not, you must know the English language.
I have to study English conversation more.
I want to use English at work.
We want rough and ready English.
I think that only people that need English should study.
For companies profiting from the English industry, it's more convenient for them that Japanese people stay bad at English forever.
You should study English harder.
I intend to do my best to study English more.
You must exercise more care in writing English.
It frequently bothers me how I am not able to use English very proficiently.
I will probably continue to not use English at work.
I don't know what I should do in order to get better at English.