You are not humanoid. Most armour will not fit you, but a smith may still be able to make armour for you for double the normal price. Magic armour will still resize to fit you

You can speak, read, and write Common, and talk to snakes.

Your base walking speed is 25 feet. You have a Burrowing speed of 15 feet and a Swim speed of 25 feet.

As a snake you gain +2 Dex and +1 Cha.

You gain proficiency in Stealth and Poisoners tools.

Your teeth are natural weapons, which you can use to make unarmed strikes. If you hit with them, you deal piercing damage equal to 1d6 + your dex modifier, instead of the bludgeoning damage normal for an unarmed strike.   

You have magic hands.

You gain Blindsight and Tremor Sense out to 10 feet.

You are... still a snake. You have a size of Small.