Hi Constantin,
The “post templates” should be used to change the layout structure and post options.
In your situation, you should base on tags and display their list of posts; for example, use the “project” tag for all your project posts and display these posts within this tag on the front page with {{#getPostsByTags}} helper https://getpublii.com/dev/getpostsbytags-helper/#new-syntax-034
Hope this helps.