Is there anyone with a not official NUS navigation guide that is more detailed and suitable for freshies like me
By navigation guide... I suppose you mean getting around NUS?
You can try downloading the app "Singapore Maps"(the one with a right arrow logo) and search for parts of NUS. I find this map rather useful and clear with its orientation. Plus, it can also indicate your current location. It's quite useful in finding out the general location of a particular building/place(i.e. S17).
Otherwise, you can try "Around NUS". But I feel that the maps used in this app is rather small and you can't seem to rotate the orientation nicely as the previous app.
For internal shuttle buses, you might want to download "NUS NextBus". It uses your current location to determine the nearest bus stops, and show the ETA for the next 3 buses as well as the buses(e.g. D, D2, B1 and B2 for UTown) for a particular bus stop.