How can I kill Sectopod? I have played a ground mission for 5 hour and the last enemy is Sectopod, I can't defeat him.
What are your assets? Heavy armor requires specific resources to overcome. Hellerium grenades, HEAT (High Explosive Anti-Tank), white phosphorus shells, cannon, or failing that flasks of acid or the trusty metal mace. Unlike every other version of X-Com and XCOM, volume of small arms fire will never bring down targets with that level of armor in X-Piratez.
Also, as I am unfamiliar with many of the endgame foes, make certain that the target is not flashing colors when you hit it. That indicates that it is shielded, and you will need to bring down the shield with concentrated fire (small arms actually will work here, and are often the best option) before you can apply damage to its chassis. You can hit CTRL+H after firing on it to see what the status of the shot was. "=>" means miss, "0" means a hit for no effect (shields will also be displayed this way, but you ARE depleting them), "hit" means you scored at least a single point of damage, and "HIT!" means you did significant damage.