How can i replace my php files (from Google map to OSM)

Hi , I recently use google map on my real estate wordpress sait as location marker because my plugin (essential real estate) support and just works with google map , now for some reason dont want to use that . I want ask u where i have to start to changing my api and how should i start with low average knowledge development. There is my samples from this plugin and marker link text

I really appreciate that if u help me a bit.

Sorry for bad English ...