A question, please, in keyboard shortcuts f1

This is not a good question - we cannot work out from that little what you are trying to do.
Remember that we can't see your screen, access your HDD, or read your mind - we only get exactly what you type to work with - we get no other context for your project.
Imagine this: you go for a drive in the country, but you have a problem with the car. You call the garage, say "it broke" and turn off your phone. How long will you be waiting before the garage arrives with the right bits and tools to fix the car given they don't know what make or model it is, who you are, what happened when it all went wrong, or even where you are?

That's what you've done here. So stop typing as little as possible and try explaining things to people who have no way to access your project!

Use the "Improve question" widget to edit your question and provide better information.

F1 is usually reserved for "Help" (screens); ctrl-F4 is used for closing the current window; and "opening" a form depends on the context: e.g. popping a form on the selected row of a grid (say, F2 - edit).

http://csharp.net-informations.com/gui/key-press-cs.htm

use a global var like "currentForm"

and write a function 'toggleForm"
when you press F1 :
fill "currentForm" with the new current Windows
open the new current Windows

and when closing this Windows by f1 or else, unload the global; var



you can create an event handler in the new form to show,