You should choose a distro where you don't have to do a lot by yourself, since you are new.
Another Point is software availability. Since it seems you want to use some specific software, check if its available as a flatpak (in which case the distro doesn't matter as long as the distro supports flatpak), or if it is directly available in the packages of the distro.
For concrete recommendations: as lembot_0004 said, debian and ubuntu are good general purpose starting points, but since ubunti updates some stuff a bit faste than debian and has a 3rd party driver installer, you might want to choose it if you have the need for it (for example if the current debian version does not support your graphics card yet).
I personally use linux mint, which looks more like windows on the desktop than debian or ubuntu.
Other people here have also recommended fedora, so if you want, you can check it out too.
First of all, review it yourself. By reading it again and thinking about it you might find some stuff.
After that try static analysis tools like olap said (even some lsp (language server protocol) integrated in your editor can give you good tips).
Only after those two options i would even consider using llms, but finding a community of people that are about your language/framework can yield better results. Especially if it is a small project.
You probably enabled home directory encryption on install. If you do that, your personal files get stored in the .ecryptfs folder, and get decrypted at runtime.
So maybe doing an ncdu inside your home folder reveals some big files there.
And honestly, if you have the time for it i recommend a reinstall with no home directory encryption but full disk encryption. That way you don't have to deal with ecryptfs since you whole disk is encrypted and mounted as one single thing.
PS: I had problems with ecryptfs when i wanted to install something with a very long folder name, which is the main reason i now use full disk encryption.1
What is that cowsay file?