Please Help - From 1st to 3rd Page GMB

Hi - all. So, I have a newish GMB. It was climbing steadily. I went from the 3rd page to the 1st page for all my major keywords in a month. I even made it halfway up the first page for a keyword. About two and a half weeks ago, I wake up to drop to mid second page for a keyword. And several spots on the first page. Now, I wake up today, and I'm on page 3 for everything. I'm freaking out. Did I catch an algorithmic penalty? I'm a law firm. I was actually getting good traffic and was getting calls regarding cases from clients.

The website above me have done nothing with SEO. They've barely built backlinks. They never post to GMB. Some don't even have pictures. My speed is a bit bad and I'm working on correcting that. But still.

Is there anything I can do? Any thoughts? I did not see a manual penalty in GMB.

Should I post my website for further guidance? I'm new obviously, but I generally don't see people do that here.

Many factors can cause rankings to drop in Google. Most frequently, we see drops because of changes that were made to the website, but they can also be caused by an algorithm update, technical issues, improvements competitors made, SERP lay-out changes or a Google penalty.
See : https://www.contentkingapp.com/academy/ranking-drop/
It shows you more details about why google ranking dropped and how to recover with some steps .

Steps to rank from page 3 to page 1 ,

Find underperforming keywords.
After Pick that keyword to rank higher .
Figure out why you're being outranked.
Beat the other pages where it matters.
Track rankings.
Repeat for other keywords.

Hope this Helps !

Speed is now a very important ranking factor. It's possible the Google update hit you hard because of this.