how does this card atk 2 times in 1 trun CHTHONIAN EMPEROR DRAGON

im not suer how it atk 2 times in 1 trun

It's a Gemini monster, so you have to re-summon it once it's on the field in order to use it's effect.

When you first summon it it will be treated as a Normal Monster. This doesn't mean that you can summon it again in the same turn except with a card effect like Double Summon, Ultimate Offering, etc. So if you do not have a card like that, you must wait until the next turn and then Normal Summon it again, and then it will gain its effect. Again, if you do that, you cannot Normal Summon another monster.

Question answered, so topic closed.

Don't forget that if you special summoned it, you can normal summon it at that case but you still won't be able to normal summon or set a monster this turn but you can still special summon monsters by a card effect or by a card that states that it can special summon monsters.