Hello @vedappan
Thank you for contacting us, It seems you are using NewsPaper theme by tagdiv, The tagdiv recommends the mobile theme add-on plugin to add AMP compatibility.
You can learn more about the Mobile theme add-ons and configuration required in their documentation
Regarding Excessive CSS, AMP pages have a limit of 75Kb CSS per page, the AMP plugin for WordPress removes excessive CSS using CSS tree shaking.
Although some third-party plugins or themes may add some excessive CSS that AMP plugins can’t strip as they are required on the front end.
We will recommend the self-debugging sources of excessive CSS using Developer tools
Goto AMP->Validated URL-> Look for URL causing Excessive CSS -> Open details -> scroll down to check CSS source with red highlight

When you find the source of excessive CSS, suppress it if not required on AMP pages or look for an alternate plugin using an ecosystem
I hope this helps!
@vedappan As we didn’t receive a response I’ll mark this as resolved. Feel free to open a new support topic if you require any further assistance.