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Yes, for VirtualBox to adjust the virtual machine execution to the full window size, the following steps must be followed:
Enable the scaling mode in VirtualBox so that the content of the virtual machine is adjusted to the size of the window. To do this, within the menu offered by VirtualBox at the top of the window, select the Scale Mode (Host + C) in the View tab.
Maximise the window size.
Adjust the screen resolution of the virtual machine so that the icons and fonts look sharp. For this last one, inside the virtual machine, click on System > Preferences > Hardware > Displays, and choose the resolution that best fits your screen.
It is common that when changing the access point from which our laptop accesses the Internet (for example, from the router at home, or a WiFi access point at the university), the virtual machine temporarily loses the connection to the Internet. To re-enable this connection from the virtual machine, we can carry out the following actions:
$ ping google.com
Using both alternatives, we also check that our equipment is running the name resolution service (DNS) correctly
$ sudo dhclient -v -r
$ sudo dhclient -v eth0
With these commands, we request from the virtual machine to re-establish the network configuration of the eth0 interface using the DHCP protocol (Dynamic Host Configuration Protocol)
In case after following these steps the virtual machine is still not connected to the Internet, the next step is to check if the virtual machine is running the DNS service properly. This can be done in the following way:
$ ping google.com
$ ping 8.8.8.8
In the event that the output to this second ping is satisfactory (i.e. that we obtain a response to the ping), it indicates that our virtual machine has an Internet connection, but that the DNS service configured is not working properly. To solve this problem, simply modify the configuration of the DNS service used by your machine. To do this, edit the configuration file found in the path /etc/resolv.conf, and modify the IP address of the DNS service that appears with one of a public DNS service (for example, using the IP 8.8.8.8.8). So when you read the file, the output looks something like this:
$ cat /etc/resolv.conf
nameserver 8.8.8.8
If, after following this procedure, the virtual machine still does not have Internet access, you will have to shut down the virtual machine, restart VirtualBox and start the virtual machine again. In this way we avoid that some process has been hung up and is causing the lack of Internet connection. This case is common when instead of shutting down the virtual machine you switch to VirtualBox Pause mode.