I'm slowly going insane. All other image editing programs have issues, so I switched to GIMP, that at least seemed to have all the features I need. But whenever I try to actually do something with it, it behaves in all kinds of crazy ways.
One example: I open an image, choose the "rectangle select tool", make my selection, then click drag from the middle of that selection and instead of moving the selected region's pixels, I instead move the region itself, the rectangle. Ok, that's unexpected, but there's a "move tool", so I try that. I activate that tool and click drag from the middle of the selection again and finally the pixels move… but also everything around it. It just moves the entire image, completely ignoring my selection. I usually get it working at some point by spamming Ctrl+C and Ctrl+X and then pressing Ctrl+V, but even then it often just randomly disappears later when I copy a different selection. I've also heard to right click and select "Select"->"Float", which is weird, but sometimes works, until it completely disappears again once I do the same with the next selection.
A basic thing like moving a rectangular selection should usually be easy, but I just can't do it. And this theme continues throughout all features of GIMP, for example I can't manage to draw half-transparent pixels, there just is no transparency slider in the color selection (even if the layer has transparency activated).
Do I understand something wrong about the concept of GIMP? Or is there a secret setting somewhere labeled "turn off insanity mode"? Do I have to hold down Ctrl, Shift, Super, AltGr, Fn and Caps Lock while dragging? Is there some "GIMP for dummies" tutorial?