Hello, the damage formula is here: http://help.goldenbattles.com/help/en/Fight_Information
And you have to pay special attention to the Note 3:
Note 3: 50% weapon damage is always hit in PvP, when hitting aliens without vulnerabilities or when hitting vulnerable aliens with the appropriate weapons.
-The prestige, HP, EP, stamina, stamina max., are your stats.
-The weapon attack is the phisycal or electromagnetical attack of your weapon depending if you are hiting a phisical or electromagnetical attack (usually its allways physical). You can see the value on your inventory or market. For a pistol grade I physical attack its 200, electromagnetical 0 because only can do physical attacks.
-The armor defense is the alien PD value.
-The PP are your practice ponts.
-The DP are 0 because aliend dont have defense points.
You can use a damage calculator like this one: http://forum.goldenbattles.com/forum/posts/list/713.page