At my first professional experience, just coming out of university and with no experience on Android. And the company put me doing a port of a VoIP lib of a Desktop application in C++, to be used as a mobile lib for Android app. At that time C++ wasn't supported by the Android ndk.
So my work was learning about android ndk, learn about jni, find out a solution for the non supported C++ in the ndk and learn about a proprietary lib for VoIP.
3 months later and with a lot of help I was able to put it to working (forget about performance). Still they told me my work wasn't good enough and I should have done a better job. For a noob developer that was hard to take.