I am a maths student and I learn both maths and computer. Now I’m more interested in computer. But in our school,teachers do not teach us much about theories,not to mention practice.I want to learn more and improve my expertise no matter how much it takes.
Are you a high school student or a university student? Are you an int’l student?
At the high school level or even at the college level, “expertise” is not expected. Expertise comes with experience.
I’m a university student from China.
Coursera, EdX, MIT ocw 
Thank you for reminding me of that mistake.
Thank you.
I’m commending you both on your attitude and on the fact that you adjusted your language from a previous post. Well done!
In an earlier post you referred to yourself as “girl.” Other people corrected you. In this post it’s clear that you learned the right approach. In the US the custom is to call any females over age 18 “women.” And in our professional world we formally attempt to ignore marriage status and age. We do our best to treat different genders and races equally. In real life, however, we can’t help but see those things! Professionally, in writing, you would present yourself as Ms. Firstname Lastname–Ms is like Mr in that it doesn’t show whether we are married or not. If you’re trying to improve your computer skills, you might say: “I want to be the best computer programmer.”
Your English is really great. I sense that you had a British teacher, because in Britain they say “maths.” In the US we say “math.”
With the kind of dedication that you’re showing, I won’t be surprised if you succeed in becoming the best computer programmer!
Thank you for your compliment.To tell you the truth,my English teachers are all Chinese. I almost learn English on my own.I’ll strive to be a good programmer.
What aspect of computers are you trying to learn more about? If you’re looking to learn theory then there are plenty of courses on EdX, MIT OCW, Coursera, etc which you can use to teach yourself. Additionally computer scientists tend to post free PDFs of textbooks so ou can look for CS theory textbooks online if you want to go that rout.
If you’re trying to learn more about programming itself the best way to learn is probably “by doing”. Pick up a language (Python or Java are where I recommend you start if you don’t know a language already), learn a bit of the syntax, and try to tackle some projects. You can check out project euler, codingbat.com, other university websites, etc for project ideas.