@vitabor
The user password is root /hadoop but you are advised to change it immediately and thereafter run the
# ambari-admin-password-reset

This will enable you to successfully start the ambari else you won't have access to the ambari UI port 8080
If using the sandbox after the above procedure I suggest you shut it down and reconfigure the network so you can access it from the host class "C" network 192.168.0.x use the Bridged Adapter and select the appropriate network whether wireless or your Cable LAN I suggest disable Adapter 2,3 and 4
Virtualbox Network setup
Once you restart the Sandbox it will pick a local IP which you could use to access Ambari i.e 192.168.x.x:8080 also remember to update the sandbox /etc/hosts file with the new provisioned IP address
HTH