Page speed
How long your page takes to appear and to become usable. It counts in Google and counts more with the person waiting, thumb hovering.
Google measures three things: how long the main content takes to show, how long it takes to respond to the first tap, and whether things jump around while it loads.
For local businesses the killer is always the same: huge photos uploaded straight off the camera. A five megabyte photo takes forever on a phone with bad signal, which is where your customer is.
The rest of the optimization pays far less. Fix the photos and you have fixed most of it.
What to do about it
Run your site through Google PageSpeed Insights, which is free. Look only at the mobile tab.
Other words about the same thing