How did you format the Laptop ?? 

if you performed factory image restore that it loads the same image on the machine. Most common cause of high ram usages on Dell machine is bloatware Dell installs on the machine. Before attempting the final step. Please remove. 

1. SupportAssist. 

2. Dell mobile connect 

3. Dell updates

4. My Dell 

5. Dell customer connect 

6. Dell Cinema

7. SmartByte 

8. Dell power manager 

9. Any other apps you don't use. 

10. Open Task manager > Start up > Disable everything except your security software and WaveMaxx. 

11. Open : Setting > System > Notifications and disable everything

12. Open Settings > privacy > background apps > Turn off 

If none of the changes work, do not use Dell OS media any more. This time Format your Laptop using Microsoft Image. use media creation too to create a bootable image. This image is a clean Copy of OS without any customization from Dell. Per my experience the RAM usages will remain between 2-3 GB with this image. As far as Dell bloatware is concerned, you only need SupportAssist. 

https://www.microsoft.com/en-in/software-download/windows10

I have 8GB

How much RAM do you have?

Well, with 8 GB it’s not unusual that utilization could routinely be 60%.  Unused RAM is wasted RAM. You want it to be used. 

I also agree with XPS_Man that clean installing Windows is helpful. It lets you avoid a lot of bloatware and unnecessary processes.

After a clean install, you can also spend time uninstalling unneeded apps and disabling services that don’t apply to your needs. All that will help to make your system leaner and faster. 

Thanks for your kind suggestion

I will check the steps suggested by you

Note

Laptop format was done by Dell Service center so i am not sure qbout the image.

Also just for information i am using 8 GB RAM

Thank you for your suggestion.

I will check it and hope it will improve.

dell service center would obviously use Dell image. Use the image created by Media creation tool