Hey there, @sebseb 
Thanks for sharing. I recommend you take a look at this Build Performance Pro Tips and Debugging Site Builds.
If you are still having issues after following those steps, please respond with:
- Your site name and site ID (we need these to dig in further on our end!)
- The issue you are encountering and what you are aiming to resolve
- the steps you have already tried / guides you have already read (this will help avoid repeat suggestions!)