layers panel is black and illustrator freezes after clicking layers panel

​@Precious_Cascade57b3 If I remember correctly, when I worked for a phone directory company many years ago, our cartographers worked with thousands of vector objects, clipping masks, paths, symbols, and grouped elements. When Illustrator has to process that many objects, the Layers panel can become very slow or even appear to freeze. Have you tried creating a new Illustrator document and then using File > Place to place the PDF instead of opening it directly? Sometimes placing the PDF can be easier for Illustrator to handle than importing every object into the document structure immediately. BUT, if you place the PDF, Illustrator may treat it more like a linked or embedded object, but if the goal is to edit every road, label, and vector shape, you'll eventually need to expand or open the artwork, and the complexity issue may return.

You could also try opening the PDF in Acrobat first and saving a copy, or exporting a smaller area from OpenStreetMap to see if the issue is related to the complexity of the file. If a smaller PDF works normally, that would point to the original PDF being too complex rather than a problem with Illustrator itself.​‌

If you're able to share the OpenStreetMap link you're working with, I can try testing it on my end as well. That would help determine whether the issue is specific to your system or if it's related to the PDF itself. Given how complex OpenStreetMap exports can be, it would be interesting to see whether the same behavior occurs when opening the file in another Illustrator installation.