It may help to diagnose the problems here in the forum if you post the exact model number and specs such as total amount of RAM, type of drives HDD/SSD you have installed, the OS, What specific software is causing the slow down, have you made any changes or installed any updates and was the system running satisfactorily until recently?
My desktop I bought it less than one year and still under warranty it's running very very slow, I called the customer support they told me that it's a software issue and they will send me an email to contact the software company that I have to pay first and then they will call me to help me with the problem!!!!!! I bought this computer less than one year and I have to pay for the software issue. Why I should I pay for that. Every computer that I buy from dell usually lasts two to three years I will never buy this product anymore and waste my money. THIS IS  NOT  RELIABLE  AND A WASTE OF MONEY.  
WORST COMPUTERS EVER