I have downloaded Android NDK from here:
for Linux 64-bit (x86). It is a ZIP file that i can extract easly, but where should i extract/install to get Android NDK functioning?
Well, downloading manually NDK might be not good options for beginning.
I highly recommend you to follow these tutorial: https://developer.android.com/ndk/guides/index.html
If you still feel get stucked, check this topic: https://stackoverflow.com/questions/7899740/android-ndk-tutorial-guide-for-beginners
Android NDK is available as a zip file here:
and after unzipping it, there are many sample program you can build within it.
In the past the way of using the NDK are documented here:
For the latest version I have extracted some samples here:
which you navigate and compile the samples yourself.