-How many objects (buildings, units, wild animals, trees) does the program have to handle?
It depends on your design. I have about 40 different types of buildings and all in all about 120 different graphics (x4 for rotation) for them, so it's quite much. We only use few military stuff, so 10 units per race are enough. There are no wild animals, and the trees will be blitted. So it depends on you, you can use 500 different units if you want to, but it's senseless. A good mix in design is essential.
-What would be the best way to handle the Map? (Maybe 2 Layers - one for Water,Sand,Grass...
We use a 2d array with 3d-polys as the ground and the buildings and units are blitted above. So you need something like this :
typedef struct SData
We used this solution, because the tiles are really small and there will only be big units, so more than one unit per tile is no allowed. I guess you use 2D, so it's quite simple.
-What kind of Info is needed for the Units? (Type,Position,Status,Target,...)
It depends on you again. What kind of pathfinding do you use ? The things found there are needed, but some more information, for example the frame of the animation which is shown and into which direction, the object is rotated. There might be some more important information needed, but this depends on you again.
How do you get data of about 80 megs ? Getting about 5 megs is possible, this is much, but not more. You should try to keep all possible data in one array, for example the multiple layers. Create some constants for each possible ground tile and simply use an int using this way.
Then for example :
Data->Ground[i][j] = GRASS_1;
Data->Ground[i+1][j] = SEA_1;
Data->Ground[i][j+1] = SEA_2;
Data->Ground[i+1][j+1] = GRASS_2;
Creating some water over green grass is useless, so you can easily save memory using structures like this.
Wieso, C/C++ ist doch relativ leicht, einfach ein Buch kaufen und innerhalb kürzester Zeit ist man drin. Übrigens, bin auch "erst" 17.