I tried to do it with the decompilation setup tool but in the end i only have the tools folder, nothing else, and in the INSTALL.md on github its for pokeemerald, not pokeemerald-expansion. How do i do it exactly?
For starters, you don't "decomp" the Pokeemerald-expansion.
Pokeemerald-expansion is a project that makes use of Pokeemerald, which is a full decompilation of Pokémon Emerald.
"To decompile" means to take code written in one language and translate it to another language, one that is easier to work with.
Secondly, the instructions to build the Pokeemerald-expansion are the exact same ones you'd follow to build Pokeemerald, or basically any fork of it, or project based on it, except for very special cases such as Pokeemerald-speedchoice.
And thirdly, if you only have a "tools" folder and nothing else, either your download didn't get completed successfully, or you downloaded something else.
Also, instead of "downloading it", as in getting it from GitHub.com, you really should be using
git clone from your terminal instead.
