There is nothing you can do your self to upgrade your system.
There are a few (very few) techs who have the skills to replace the Flash chips and know how to program them so they work. It won’t be cheap and the resale value won’t be any better than what your system came with.
for a lot less you can get physically small drives which offer quite a lot of storage.
RAM is what you have you can’t change it. Lastly the other option is locating a used system which offers what you desire, buy it and then sell your system once you’ve transferred your stuff over.