If you start to notice things are a little different than they were when you were trained, it is due to changes made by theme and plugin developers during improvement/updates. Every time an update is pushed out, there could be changes to performance, function, and/or appearance. This can be frustrating, but these changes are necessary to maintain the integrity of the theme or plugin. If a particular plugin is causing you grief, you can go to their site and chat with their support team who will have resources to explain the new changes.