I just solved the issue, check the edit in the comment above.
Thanks for asking tho. I did indeed re-ran the setup (build.gradle and genIntellijRuns) several times, it was just that i wasn't looking in the right places.
Also thanks for the link, it'll come handy later. I already know the basics about Java, OOP and the syntax (i think that's how it's called in English?), it's just that i don't have much experience and i'm also new to Intellij (was using NetBeans previously), but the other in-depth forge information will be really useful!.