Hi Marco!
Sorry you are experiencing slowdowns while authoring in Storyline!
Testing it out on my end (SL ver 3.73.29831.0 within Windows 11 Parallels on a Mac M1), the speed and performance seem to be functioning properly and everything worked normally!
Just to confirm, are you working/saving off of a local hard drive? If you are, I would suggest performing a repair to see if that speeds things up again.
If still unsuccessful I'd recommend connecting with a Support Engineer so they can take a closer look at your project file and see what the issue could be.
Hope this helps. Thanks for reaching out!