Hi @Yoakin ,
If you Link the Mesh Data of one Object to another, then both Object use the same ‘list of Vertices’ Positions and how they are connected via Edges and Faces’.
Here Suzanne uses the Mesh Data of the Cube:

So you can’t keep that change you want.
You can Link other things, like Materials, so both Objects can look different (have there own Mash Data), but use the same Material.