Please help

I installed Ubuntu on my whole harddrive, wiping everything that was on it already. I used the amd64 iso version of ubuntu then i successfully installed and booted into ubuntu and it was running very fine. But then i mistakenly delete a 500 mb partition which was /dev/sda1 and it's mountpoint was /boot/efi and since then everytime i start my laptop the only thing that appears is a small dos like window in the middle of the screen which has two tabs "boot menu, app menu" boot menu has one entry "ubuntu" and app menu is empty whenever i press ubuntu my screen just refresh.

But the real problem is that i can't even get into my boot setup menu with f2 key when my samsung logo appears i press f2 and it says please wait... Like it normally do but then it just brings me to the bootmenuappmenu screen, even i am unable to boot any dvd USB anything...