How to see how many related videos people view?

Hi there,

I've stepped into a marketing role at a startup and have gotten a couple questions from my CTO I was wondering if someone could help me with.

We are a customer video review platform and there are two things we want to track. We work with brands to help them collect video reviews from their customers, which we then host on a landing page. You can see an example of this here.

Apologies in advance if these questions seem kind of nebulous. I am not a technical expert.

FIRST - the average session length for people tho start on a video page that is shared from social media

From my CTO, if the page "has ?s=…" at the end of the URL it means it was socially shared

So, I created a segment in Google Analytics “Socially Shared Videos” for referral path contains “?s=” - this has shown zero users since January

I figured that theoretically, you should be able to look at this segment in Audience > Overview section and see the average session duration.

However, as I mentioned, this segment does not show any users. Is there something I am doing wrong here?

SECOND - How many related videos people watch? How man total watches are generated from related videos and the average number of related videos watched per person?

There is a lot in this question, I realize.

Let's take our example page again.

We are planning to put "related videos" on these pages. The assumption I am making is that users will stay on the same page while watching these videos.

Is there something that I can do in Google Tag Manager to look at how many of these "related videos" people watch? How many total watches are generated from related videos? The number of related videos watched per person?

Thanks in advance. Let me know if you need any additional context to answer these questions.