am i able to fix this problem?

so i've been having this issue since yesterday, i got simpsons hit & run back and modding my stuff and i got this. file is a read only file and cannot be saved can i fix this issue?

Is this in the game directory? You don't need to, and shouldn't, be modifying your game folder

You should make a mod (Here is a very basic introduction
But to summarise:
Make a folder for your new mod in Documents\My Games\Lucas' Simpsons Hit & Run Mod Launcher\Mods\
Provide a basic meta.ini

[Miscellaneous]
; The actual title of the mod displayed in the Mod's list.
Title=Example Mod

; The name used internally to refer to the Mod.
InternalName=ExampleMod
; use custom files to modify files
RequiredHack=CustomFiles

Then make a folder "CustomFiles" where you'd put a copy of the game files you want to modify.
E.g. to replace leveli.mfk for level01 you'd make the folder "CustomFiles\scripts\missions\level01" and copy leveli.mfk from the game there.
And modify that copy

Hope that helps get you started!

this should help, thank you