1-Download Odin Flashing tool 2-Download TWRP recovery md5 file
Here3-Download Samsung and android drivers
Here4-Connect your ace 2 via usb cable with laptop or pc
5-
Open Odin6-Put your phone into download mode ("Vol Down + Home + Power").
7-You will see yellow sign on up left mean that you are connected
8-In PDA section select MD5 file you downloaded
9-Hit start button
10-your phone will reboot and all done