I bought a new iphone x about 4 month ago. Suddenly. went my phone in water from my hand and its gone off idont know what happened with it ita water resistance

The iPhone X is not advertised as waterproof. Only Water resistance to a certain extent.

Submerging in water is highly discouraged, and water damage is not covered by warranty.

About splash, water, and dust resistance of iPhone 7 and later - Apple Support

To prevent liquid damage, avoid these:

• Swimming or bathing with your iPhone
• Exposing your iPhone to pressurized water or high velocity water, such as when showering, water skiing, wake boarding, surfing, jet skiing, and so on
• Using your iPhone in a sauna or steam room
• Intentionally submerging your iPhone in water
• Operating your iPhone outside the suggested temperature ranges or in extremely humid conditions
• Dropping your iPhone or subjecting it to other impacts
• Disassembling your iPhone, including removing screws

tell Apple - the users here have nothing to do with APple warentees

Contact Apple support of the vendor who sold you the new phone

LN