Well. Loooong journey.
Remove the AC and AC compressor as well as the climate box inside your dashboard and build a custom venting system
Carbon dashboard
Remove all not needed wires (that's already easily 10kg/22lbs)
Remove everything Audio, Airbag, GPS, Radio, ...
Replace the battery with a 2kg/4.4lbs LiteBlox battery but do not install
it in the trunk as the long cables will weight more than the battery itself.
Throw on a full Akrapovic
Macrolon windows
Carbon doors, hood, trunk lid,... (like Devotec also has it)
Get an expensive but light FIA approved CroMo4 roll cage (no cheap ST45 or ST52)
Single mass flywheel with a 2disc clutch
Plus the many many small things you do when you have every part in your fingers and start to think about if it can be made lighter or iss needed anymore.
Basically you'll have to start with a naked body shell. Getting the weight so low
is not possible by just adding plug'n'play parts.
It's many small things like: Rear view mirrors for the doors. e92 M3's are way too heavy.
That's why I use the e36 mirrors. but it's not the stock e36 steel mirrors. It's a cheap China copy of the e36 M3 mirrors made out of plastic. But it saves nearly 1kg/ 2.2lbs per mirror