How to change grid size and tilemap without breaking your game

Godot Version

Godot 4.2.1

Question

How do I change the grid size without breaking everything? I’m working with a template I found on GD Quest (The flood fill algorithm · GDQuest)

The game I want to make uses the Kenny Tiny Battle assets. (Tiny Battle · Kenney)

My issue is that I need to change the base game’s 80 x 80 grid to a 16 x 16 grid without breaking everything.

so you readjust the image size to x5 of the current one, so it’s 80x80px
can be done by photoshop, or any online tool to rescale it