How to improve my mini map in a 2.5D tile game?

Hi, I want to make the minimap like this: The wall in the minimap only shows as a 1 unit rectangle block. The player will only show as a blinking point. and the floor keep the color.

Now I followed some tutorials on the Internet using a second camera implemented a mini-map like this:

It's just a smaller version of the big map which is not expected. I googled a lot, but still no idea how to do this. The map is dynamically generated.

Any suggestions would be greatly appreciated!!!

Thank you!