1) In our future work it's very important to have a perfect command of the English language. ( =to know the English language).
2) How are you going to pass your English exam this year?
3) I've been learning English since studying at school.
4) Nowadays children begin learning English on their own.
5) You know English quite well. (Your English is good)
6) I wish I had good knowledge of speaking English.
7) Take my advice: the more you try to communicate in a foreign language, the faster you will be able to speak it.