Can I make the UI (User Interface) font bigger in Cinema 4D?

Yes, you can!

To adjust the font size, simply follow these steps:

1. Open the 'Preferences' window by clicking on 'Edit' in the top menu, then selecting 'Preferences' from the dropdown list.
   
   
2. In the 'Preferences' window, navigate to 'Interface'
   (It should already be selected when the preference window opens)
   
   
3. Find the 'GUI Font' section. Click on the small dropdown arrow next to 'UI Font' (Mac) Segoe UI (Windows) to expand and see the font size options (Default font size is 11)
   
   
4. Choose your preferred font size from the expanded list to increase the visibility of the interface text as needed.
   
   
5. Restart Cinema 4D

Here is a screenshot of where you can find the Font settings: