My computer freezes when i start workstation on the virtualbox

hi everybody, english is not my native language. i got this problem. i already downloaded virtual box and whonix. first i got a problem because i couldnt get into uefi. a guy told me if you dont have uefi, you probable have bios. then i went to bios and enabled the virtualization. everything was fine then.

i started the gateway and it worked ok. but then when i start the workstation, my screen freezes and i cant use the keyboard or the mouse.

my pc have an Inter® Core™ i3 CPU 540 @3.07GHz 3.07GHZ
4.00GB of ram
windows 10

can you tell me whats happenin? 4gb ram is not enough maybe?? thanks in advanced