[Threshold]

'format' was placed AFTER 'TextDrawSetString'.

pawn Код:

public OnPlayerTakeDamage(playerid, issuerid, Float: amount, weaponid)
{
        GetWeaponName(weaponid, Weap, 34);
    format(astring, 256, "%s", Weap);
    TextDrawSetString(Textdraw5[issuerid], astring);
        TextDrawShowForPlayer(issuerid, Textdraw5[issuerid]);
        /* issuerid gun */

You used 'Textdraw11[issuerid]' in your TextDrawSetString instead of 'Textdraw11[playerid]'.

pawn Код:

format(bstring, 256, "%s", Weap);
        TextDrawSetString(Textdraw11[playerid], bstring);
        TextDrawShowForPlayer(playerid, Textdraw11[playerid]);

EDIT: And the additional information provided by Pottus.