Not trying to be rude but, your laptop could be that bad that it can't even run Minecraft, i had this problem that i didn't have the best cpu of even a gpu (Graphics card) but after i upgraded it worked again.
May I ask what kind of phone do you have?
Like the note 9 or the s20 or whatever
Well if you are signed in with a Microsoft account then it could be possible that you do not have the permissions to do this.
Have you paid for the realms?
May I ask what you mean by private world? Like a realm? Because if it is then one of two possible things could have happened:
During transportation (moving location), you have somehow damaged the cd or the drive of the console.
If you have a trial of realms, then it could have ended, this inevitably results in the world being deleted!
I think this is just how it works this is how it has beed for a long time also!
May I ask if you have the requirements for Minecraft Windows 10 Edition?
If you are not sure just search it up!
There could be multiple problems but with this all I could say is maybe resetting the realm? If that is even a thing