Kindly refer to the following links:


Is Prophet ﷺ alive in the grave? 


Is the Prophet Peace be upon him Alive In The Grave


Is building tombs over graves allowed, if not why is the tomb over the Prophets grave not destroyed?


Are all the Prophets alive as they prayed together on the night of Meraj?  


How did Prophetﷺ‎ see people in Jannah when he went on the miraculous night journey (Miraj)


Do Prophets & Messengers pray in their graves?


https://islamqa.info/en/answers/21524/can-the-prophet-peace-and-blessings-of-allaah-be-upon-him-hear-those-who-call-upon-him-when-he-is-in-his-grave