SharePoint 2016 runs slowly after migration from 2013

Recently, we migrated from SharePont 2013 (standard) to SharePoint 2016 (standard). But, the SharePoint intranet site is running very slowly.

Here is the configuration of the new sharing environment:

Application server:

RAM: 32 GB
HD: 800 GB
Processor: 4 cores
Operating System: Windows Server 2012 R2

Database server

RAM: 12 GB
HD: 800 GB
processor: 2 processor
Operating System: Windows Server 2012 R2

my The size of the database is 100 GB and the root site having 20+ subsitesI've tried almost everything to improve performance, but no luck. I followed the link:
https://www.networkworld.com/article/2210265/tech-primers/10-steps-toptoptize-sharepoint-performance.html

Anyone can suggest, should I make changes to infrastructure or something else?

Help appreciated.
Thank you