In case of yes , kindly share what did Bert impacted most on you website, i.e Keyword ranking, traffic of both??

Nope, made any difference at all.

Hmm, I have heard ugc have been given much preferences

That’s not BERT. UGC has been on the wane for a while and while part of the algorithm isn’t how BERT works.

This is a good starter explaining how it works:

https://www.searchenginejournal.com/bert-explained-what-you-need-to-know-about-googles-new-algorithm/

We have noticed an impact on three projects. One is related to weight loss, and the other two were from the technology niche. Keywords disappeared from SERP overnight. In-depth analysis proved that the relevancy of content becomes a prime concern to Google. 

That’s not BERT. That’s been Google’s approach to ranking for a while.