Cannot build front- and backend

I used to be able to use yarn build to build the entire front and backend but for some reason that is not working anymore. To make sure the issue is not isolated I recloned the repository on a new pc. I created a conda environment and installed all the packages with poetry as the guide suggests. If I then setup postgresql and run the server on a postgresql database I get a SuspciousFileOperation error. I saw in some other issue that this could be resolved by building everything with yarn build.

So the next step was for me to install yarn and build everything. However, I cannot install yarn for some reason. I installed node (version 18.19.0) and npm (9.2.0) and then tried to install yarn with npm install yarn. But then I get the following error:

Now it might be very trivial to solve this, but for some reason I cannot really find it online. But the dependency versions seem to be wrong and I don't know what combination of versions I should have to fix this. Also I tried installing with --legacy-peer-deps, but this led to an error when installing with yarn install --frozen-lockfile. Can you please help?