how to decompile minecraft client?

If you want to decompile a minecraft client rename the ".jar" on the file to .zip and unzip it and you should have all the game files. To get this you have to go to your minecraft game files and the version you select for example "1.15.1.jar". If you want to know how to get to your minecraft game files type in the search %appdata% > then the roaming files > .minecraft > versions. Your welcome.