Is it possible to change shortcuts related to playback speed?
Sure you can do that. Go to the Edit menu -&gt; Keyboard Shortcuts... and search for the action you want to change (alternatively search for the keyboard shortcut itself).
Click the little x on the existing shortcut to remove it. Then click the field and type in the new shortcut. If it doesn't work, click once more, and type again.
The only problem is that many shortcuts are already in use and Premiere is immediately removing the shortcut elsewhere when it was in use, so you might want to click undo after accidentally removing a shortcut. You could use the search bar to see if the key is still free or change several shortcuts to free a key.
At the top you can change the keyboard layout profile. So you can always go back to the defaults at any time, if needed.