Some Mac OS programs windows too big to fit the screen

I faced this problem not very long time ago - e.g. Zoiper for Mac OS doesn't gives me any way of reducing its size of its window - I even tried to assign a hotkey for "Window" / "Zoom" option - which haven't helped me to access interface elements of the program - which is too big.

I suppose the only solution for this, is downloading some third-party software which will allow using keyboard arrow keys to move or resize window.

Annoying problem....