There are many reasons why your laptop may be slow.  You will want to post your question in the Laptop Forum here. 

Thank you for your message.

Is the notebook slow when booting or using any particular application like the browser or a software?

Is it slow from the time you start the computer?

Run a hardware diagnostic by following this link http://bit.ly/2fJuGXB  & check if there is an error listed.

For my reference, please click on my Dell username & send a private message with the service tag, registered name & email address.