You put condition in place with no influence on function, try this
public nozik(id) {
new name[32]
new auth[64]
get_user_name(id, name, 31)
get_user_authid (id, auth, 63)
new iSize = strlen(name) - 5;
if(iSize <= 0 || !equali(name[iSize], "ADMIN") )
client_print(id, print_chat, "No access!");
return PLUGIN_HANDLED
}
if (g_match_inprogress != 1) {
g_match_inprogress = 0
set_task(1.0, "restart_round", 0, "1", 1)
set_task(2.0, "mp_startmoney", 800, "800", 800)
set_cvar_num("mp_freezetime", 10)
set_task(3.0, "strip_weapons")
set_task(4.0, "knife_msg")
client_print (0, print_chat, "%L", id, "noze", name, auth)
} else {
client_print(id, print_chat, "%L", id, "nelze_noze")
}
return PLUGIN_HANDLED
}