Steam notifications are nice, but in AoE2:DE they block the minimap. This is annoying, so let's fix it in 4 easy steps:
Navigate to C:\Program Files (x86)\Steam\resource\styles or wherever your steam installation folder is located.
Right-click gameoverlay.styles and click open with, then choose notepad.
Change the text from BottomRight to TopRight, or whatever your preference is.
Important: after the two forward slashes // type any 3 characters (exactly). In the example, i have typed 123. This will ensure the file size doesn't change, so Steam doesn't override your changes.
Alternatively, you could just turn off all steam notifications entirely in steam's settings