If a person lost his legs and then died, will this person be raised up and come back on the judgement day with no legs ? If yes, how will he/she be able to walk ?

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

A person who lost his legs or any of his members in The present life will get them again on the Day of Resurrection.
al-Qurtubi (May Allah's Mercy be upon him) said: 'scholars stated that a servant will be raised on The Day of Resurrection with his full members that he had on the day of his birth; he will even be raised uncircumicized, i.e. with a foreskin.
The Prophet (Sallallahu Alaihi wa Sallam) said: "You will be raised on the Day of Judgement barefooted, naked, and uncircumicized (with foreskin)." Then he (SAW) recited:
{….. as We began the first creation, We shall repeat it, (it is) a promise binding upon Us. Truly, We shall do it.} [21:104]
Allah knows best.