Hello my look for on pictures are excellent, web not so much

[farm gate]

Hi guys, I am pretty new to SEO stuff, I've done my job onpage seo, and offpage seo too, but after days what I found was shocking at least to me.

few pages of my website are ranking pretty good on google images, you can see the picture of the post in the 4th or 5th or 6th place on many images within my site, but I don't know why on the web my site isn't ranking well at all, not even in the top 150.

I need help to fix this and how did this happen in the first place, to understand this will give me good idea of what to do next.

most of the traffic coming to my site is from Google images which is not good because the searcher maybe wants to download the picture and leave.