You'll always read slow in a new language. It takes a lot of practice reading to begin to read quicker. You'll naturally begin to read faster as you start to become more comfortable with sentence structure and grammar. My advice, read a lot! On another note, how do you read mentally? When you begin to learn a language many students associate and translate words. As in this word means this in my language and then they understand it. However, to become fluent in a language you have to cut out the translation step, and recognize the word directly to it's meaning as you would in your own native language. This is an important step to increasing your reading skill and becoming a more natural speaker/listener and reader/writer.

A useful like for speed reading http://www.lifehack.org/articles/lifehack/teach-yourself-speed-reading-techniques.html

When you read a passage or sentence, glance through it quickly for the first time only concentrating on key words, ignoring "is, the, by" etc first... Then go through it a second time slowly. You will improve after some time of practice.