can some one please answer me if its illegal to create a real world map in a game as i am trying to make one.
No, but I believe that there’s some copyright type of things to do with buildings, I’m guessing like in GTA if you want to make a building you’d have to change it a bit if you don’t have permission.
the creation itself is absolutly not illegal,
what’s really matter is where the data you are generating with or replicating real world places came from .
for example and from memory SRTM data wich is the elevation or heighrmap data produces by NASA is OK to use, but you have to give credit to them .
openstreet map data is ok too with the same condition .
satellites images or aerial images is the main big big BIG problem :
it’s nearly impossible to find free or cheap images under 30m resultion, because it cost a looooot of money .
i am nearly sure that you can’t use google or bing images in your project (commercial or not) without permission
things may changed now, so if you find some good source of free or cheap images let me know 
i am interested for my old flight sim project 
by copying i meant that “building” a same city in UE4 all on my own (no use of any height maps or other software); is that thing legal?
how can someone get permission for making each building; i mean is it applicable to certain brands or popular building or other structures which are owned by government?.
You would not be able to create signage and specific building designs and shapes that are copyrighted.
For example, if you wanted a McDonalds drive-through restaurant, you can’t do the golden arches without first obtaining permission from McDonalds.
And many of the large companies are going to want money for licensing rights to use their name and logo and signage and product likeness in a game.
So best to not even attempt it unless you have millions of dollars for licensing.
Create your own designs, but be careful not to design anything that is too close to any real business likeness.
that makes me more clear now; but can i still copy (exact same copy) structures like houses and government properties?
Most house floor plans would not have any design copyright other than the engineering or architectural firm’s stamp, which is for rights to reproducing plans or for building an identical structure.
So as long as you varied it to some degree, you can mix and match floor plans, roofing, facing materials, change up window and door placement, etc.
There are literally thousands of house designs and shapes, most are just arrangements of various cube shapes.
You can make something similar, just don’t put any signs on it that would be the same as some major business or store.
thanks a lot!
whats the update then i also think of similar idea becuase but i m struggling to get data as osm do not have data and google poor quality data and bing high quality but less data like building position and Hight and shape these quality i mean