I have seen a lot of complaints about the gestures not working how you'd expect. They're similar to, but not exactly like iOS's gestures, which I think is what is confusing people.
To get to overview / your app switcher, you don't need to swipe up and hold, or swipe to the middle of your screen. A short little nudge and release from the bottom will open this. You can do it from anywhere on your home screen and only from the bottom in an app.
To go back, just swipe in from either side of the screen.
To open a sidebar you can either place your finder on the very edge and hold and it will pop up, or you can swipe a couple different ways - 1st way, swipe down on an edge, then in towards the center in an "L" shape. The second way is to swipe down and in, in a steep diagonal from the edge.
Try these little tips and see if they help at all!