Mobile usability issues with urls which ends with '/embed'

I noticed that there are mobile usability issues with some urls which end with '/embed' including the folliowing url:

https://www.thewordcracker.com/miscellaneous/how-to-easily-password-protect-a-website-or-subdirectory/embed/

There are three issues reported on Google Search Console:

1. Text too small to read
2. Clickable elements too close together.
3. Viewport not set

I tried to add some CSS codes to fix the issues, but CSS codes did not work.

Could you please let me know how to fix these issues?

Thanks.