I have a Dell XPS 15 9560 and it is running very slowly. When I use lightroom, it often crashed. Can you offer a solution pls.

That's not quite enough detail. If this was mine I'd do the usual canned air cleaned (what is and how to use is on the web for those that don't know how.) If that doesn't help I'd share a Web Speccy report which can reveal issues. Read how to share the link to the report at https://www.piriform.com/docs/speccy/using-speccy/publishing-a-speccy-profile-to-the-web

One of the other things I run into are clients that update drivers. Don't do that if the machine is working. After the Web Speccy report I may advise to use DDU (google that) and install the drivers that Dell issues for your machine at Dell.com using your service tag after we disable Windows 10's driver updater.