I want to buy a new lenovo laptop could you please suggest best laptop for dual booting.I am looking for Windows10+Ubuntu.What is your suggestion.I want learn linux.

Don't dual boot. Have a good host OS and then run other operating systems in virtual machines. Current systems, especially ones built for Windows, don't play nice for dual booting without a lot of effort, pain, and suffering on your part!

So it's better to use Linux through Virtual machines and other tools in windows system?

Because i want learn Linux system administration and Networking course.For practical purpose i am asking.Is it possible to do in virtual machines?