Hi ,  my experience using WIndows 10 has been issue free , but if you really want to downgrade os version here is the link to your licensing rights and other useful info like how to order disks etc , as decreed and supported by your laptop manufacturer 

https://support.lenovo.com/au/en/solutions/ht077446

however contact them just to confirm support for your particular laptop model

re WIndows 10 - if you browse far and wide over the internet , my personal maintenance suggestion is to install and run superantispyware periodically to clear the inevitable accumulation of relatively benign parasitic internet related elements - once they total over 1000 , they seem to become an impediment to smooth internet browsing