Gnome apps will usually open full screen. Other apps will maximize if you drag them up so they touch the panel.
Maximized apps can be de-maximized by grabbing their title bar with the mouse and dragging down.
Installing the Gnome Tweak Tools gives you access to the option to add minimize and maximize buttons to windows.
If you Google, you can find instructions to turn off the "go full screen when you touch the panel" behavior. That also turns off Gnome Shell's ability to snap a window to one-half of the screen when you drag it to the right or left edge.
Gnome design standards want us to open new apps in new work spaces, not minimize apps to clear out room. Middle click on an icon in the Dash and it opens in a new work space that's created automatically, and deleted automatically when you close that app.