Explain Agile to me like I’m 5 (Given the context in my post)

Hello,

So, I'm a sophomore CS student working as QA engineer at some software development startup outside US part time.
This is my first job, and my company being a startup a lot of things are a mess imo.

I do software testing here. According to the tech lead, he follows agile methodologies in terms of development.
Devs follow an SRS for initial development which doesn't get updated and clients keep adding new features. Nobody knows how is the final version of app supposed to function due to this. I had so much trouble as a tester trying to find final approved design/feature cuz there was no reference document.. this has resulted in so many bugs and issues.
Yes, they use Jira but even after an issue has been closed, I still find the same bug repeated in a different way. Logic to many features isn't clear.

As QA, I know I have to set standards, but I'm shy, scared and feel inexperienced proposing something cuz this is my first job. Besides, there's many SDLC ideas I'm deeply unfamiliar with.

I thought of updating the SRS or some intermediately doc to track changes in features, designs so everyone has some common reference point. But, I've realized, nobody wants to read something long and its time consuming too.

This is Agile? I don't understand, how can I help as qa in a scenario like this?