Is it possible to add esim to iphone X.. or is there any app that can help me with that?

This article discusses using an eSIM and specifies: "iPhone XS, iPhone XS Max, iPhone XR, and later feature Dual SIM with a nano-SIM and an eSIM.":

Using Dual SIM with an eSIM - https://support.apple.com/HT209044

It would also have to be a feature supported by your carrier service:

Find wireless carriers that offer eSIM service - https://support.apple.com/HT209096

No.

The eSim is part software, part hardware built into the Cell chip in iPhone Xs and later. There is no way to add it via software alone.