Guidance in finding ....help on taking over site. :)

Site URL: https://dogsdeservebetter.org/

Not sure in the right place but....

I am hoping to find tutorials/webinars/guides that can help me navigate better to do the changes needed on our site. Our person who had hired the gent that did the site for us has left and due to our troubling times, we really cannot afford, as a non-profit, to dish out 300 bucks each time I need some changes. So I am looking for a good all around place that, if I do need help in...format changes, adding the images and keeping the layout the same, adding pages.....(yea, almost everything,) I can head there and get the help needed.

I have done a little bit with the site but needing to get in and do a LOT more, I'm feeling a tad overwhelmed. 

Thanks for any advice anyone can give. 

Site built on the Brine Family of templates, not sure which one but that is not that important. Here are a couple of things that can help you:

https://support.squarespace.com/hc/en-us/articles/212512738-Brine-template-family

https://paigebrunton.com/blog/best-squarespace-template-brine