As your knowledge advances, you will want to take classes that correspond to the level that you are at. These will challenge you and introduce you to the more complex aspects of the language. Advanced courses are available through your local colleges and universities, but it is also possible to take online courses from reputable sources, such as the Goethe Institute. The German state strongly encourages cultural exchange and you will find that there are a number of opportunities to study there. Living in Germany will increase your language abilities better than anything else, as this will immerse you in the language and you will get to see how it is used first-hand. You can go to Germany through an exchange arranged by your high school or university, or you can apply to a university or community college in Germany. Student visas will be granted to allow you to stay in the country and tuition is much less expensive than in many other places. You may also be able to get a job and work, rather than going to school. If you are young enough, it is even possible to work as an au pair (or nanny). English-speaking nannies are coveted in Germany. Making a German friend will give you the opportunity to practice your German, get advice on pronunciation and grammar, learn new words, as well as getting to know the culture. You can chat with them online, make calls over Skype, or you can try to find a local German (such as a student at your university). Read everything you can get your hands on. Try to read at progressively higher levels, so that your vocabulary is being challenged. You can read from any source, but try to read sources that are likely to have good use of grammar and spelling. This will help you to learn the language correctly. You can read online copies of German newspapers and magazines. Examples include Die Zeit, Frankfurter Rundschau, or Der Spiegel (which tends to be of a slightly lower reading level than the newspapers). This will challenge you to understand the language without the crutch of relying...

How would you rephrase that briefly using Indonesian?
Ikutilah kelas tingkat tinggi. Cobalah belajar di Jerman. Berteman dengan orang Jerman. Baca secara intensif. Tonton film tanpa teks. Tulis.