As Julian said you can also take online courses, but of course this is not the best way to learn a language.
If you have the opportunity, you should take a course in a German speaking country, such as Austria, Germany or Switzerland. This would certainly speed up the learning process.
I would be happy to help you to find the perfect school for you. If you want you can contact me under UK: +44-2033555340 | US: +1-800 6136345 | Int: +34-932688774 or send an email to firstname.lastname@example.org.