It’s not very clear from your post, but I’ll assume you are modifying a symbol in KiCad, not a footprint or looking for physical parts.
Starting from a copy of an existing symbol is a good way to start learning the symbol editor.
Grids work the same way as in KiCad’s other editors, each of KiCad’s 4 editors has it’s own grid settings in the preferences, and grid overrides. You can also place lines off grid by holding the Ctrl key. This is all very much beginners stuff and explained in more details in a lot of beginners tutorials. You can place graphic items to whatever you like, but please always place the pins of symbols on a 50mil grid.
Can you explain:
You changed the grid, and what is it that you want to fix now?
Also:
KiCad’s default libraries are read-only. Do not mess with that. The easiest and quickest way to start editing is to first place a symbol on the schematic, and then press [Ctrl + e] to load it in the symbol editor. (Just close the symbol editor when you’re done, KiCad prompts you to save the changes back to the schematic). To do it properly also needs a bit of library management, but that can be postponed to some later time.
Just curious, are you in the same class as: