Freezing issue latitude 3490

Hello

I have bought my laptop Latitude 3490 about a year ago. At first everything was fine until about 2 months after, in middle of working, it got turned off on its own and then start restarting itself for so many time. (I think around at least 10 times). When it finally turned on, it asked me for a "BIOS password". To that they I've never heard of it before. So, after talking to DELL technicians, I had to do a clean installation of Windows 10. After that the performance became really slow. To open a PDF it would takes about 2-3 minutes. Or when 2 or more windows are open and I want to switch between those everything stops moving, the music I listen to become a noise. after less than 5 minutes it switch. At first It wasn't like this so I just updated the windows through "Windows update". Because it got worst I contacted DELL technicians so many times and every time, everyone told me to it only need updates. But there are no more updates in the list and day by day it is getting slower and slower. Most of the times it freezes and I have to force shut it down. It happens at least once in a day. Some days ago. Sometimes happens 4 times a day!. then "Blue screen error" occurred. I have used "Support Assist" to troubleshoot but it gives me the message that everything is fine. But I can see something is wrong. 

What can I do? Send it to company to repair or replace it? I am totally dissatisfied with this product!

Thank you