virtuabox e screen

Installed virtualbox finished installing os virtualized I try to switch to make the video image fit the screen but nothing happens, it could be a kernel problem, I use Tumbleweed

Do you use Tumbleweed as a Host or as a Guest system (or both?)
To be able to resize the screen image the Guest OS must have the Virtualbox Guest Additions installed. OpenSUSE images should install those additions automatically when they detect a virtual install, unless something is broken or you use incompatible versions of VirtualBox and Guest Additions.
Other OSs need a manual procedure to install those additions, see the User Manual here for details.

Maybe I explained myself badly, my operating system is Tumbleweed, kernel 5.1.7.installed virtualbox, with zypper install virtualbox, also install guests, the problem that installed in virtual os Debian, when I try to adapt the image to the video I it always stays small, tried with ctrl-a ctrl-f, but nothing to do always lrimane to a small resolution, how can I do to solve the small screen problem, thanks

You have to install Virtualbox Additions in your Guest.
Unlike openSUSE which installs all Guest related packages when the install detects the install is in a virtualized environment, all other distros including Debian require you to install Guest Additions manually.

When I do a search on my Debian, I get the following packages you should install (list edited to remove what I feel should not be installed)…

apt-cache search virtualbox-guest



ok thanks