[Jithu]

format(string,sizeof(string),"You have killed %s. You now have %d kills.", GetName(playerid), PlayerInfo[killerid][pPaintBallKills]);

i think This should be like this

format(string,sizeof(string),"You have killed %s. You now have %d kills.", GetPlayerName(playerid), PlayerInfo[killerid][pPaintBallKills]);

try to add GetPlayerName instead of GetName....

did you add #include <foreach> before?

Try PlayerInfo[killerid][pPaintBallKills]++
instead of
PlayerInfo[killerid][pPaintBallKills]++;