iPhone X slightly bent

If it's considered to be accidental damage and you do not have AppleCare+, it'll be 549$ for a complete replacement. Assuming you are in the US, pricing depends on country.

https://support.apple.com/iphone/repair/service/pricing

Apple do not repair case, they will replace the whole iPhone for a fee.

Make a genius bar appointment with Apple for an evaluation.

They have diagnostic tools and can tell you what options you have.

The first consideration is... How bent is slightly? If it does not impair function and usability you may be better just to accept it, because it WILL be a chargeable non-warranty replacement.