wrong thumbnail appear on google search. how to resolve this?

Hello,I've got some issue that i'm trying to resolve.I've set on almost each page in my site an image that should loaded when the page shared in social media, and although it works on facebook etc - on google search results it always loading random image.how can i resolve this? as it always picking the not one of my favorites.link to site www.roitmanphoto.com

I think you should add following code for image.

< meta property="og:image" content="siteurl.com.jpg" / >

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