This channel is a great place to learn Fusion 360. Start with the beginners level series of 16 tutorials which take you from the most simple to slightly more complex parts. These standard parts have a lot of the features you find on basic prismatic and blocky engineering part shapes. About 20 hours should be enough time to work through the 16 basic tutorials at your own pace and then many find that they are able to prepare some of their own designs for 3D printing or other processes. More beginners tutorials are here and some intermediate level for those who are keen and want to go on.