LandJ:I already finished the Road to Serfdom.
You might be interested in these: here and here.
-What do you suggest me next? -Should I continue reading libertarianism from a philosophical point of view or it is OK to start reading economics?
See here (each of these has many links within, which are also good):
Recommendations by category
What is the best book written on the current financial crisis and its origins?
Where to learn Austrian economics
One Book for Capitalism
I am interested in reading Economics in One Lesson by Hazlitt. Do I have to know Basic Microeconomics and Macroeconomics in order to understand Haziltt's book?
Not really. It's pretty geared toward the layman, but keep in mind it was published in 1946, so it's a bit more sophisticated than "layman" books of today (i.e., you might need to pay a bit more attention, as the vocabulary and sentence structure is more complex than a lot of people are used to).
I recommend the Second Edition (1978), for reasons mentioned here. You'll only find this version in CD (audio) format in the online Mises Store, so you'll probably have to go to Amazon if you want a hard copy. But you can still have some of the money you spend go to the LvMI if you simply make your purchase through GoodShop, as described here.