viewport

Hello everyone, I am new to Hammer Editor and map-making, and I need some help with this viewport problem I had. So when I opened Hammer Editor and looked through the viewport, I saw a full-screen button at the top and so I clicked it, and now I don't know how to make it smaller again. Does...

So i want to make my viewports bigger, because how its now i cant really work. I have it now like this: https://imgur.com/a/Luhj3 But i want it kinda like this: https://imgur.com/a/ShF4h Any ideas?