My internship was a great experience for learning about the markets and how they work, how we interact with them, and how companies and individuals invest their money, I was involved with making attribution and cash flow sheets for many of our funds, which I found to be an interesting way of learning about the industry.
The work is pretty simple, for the most part I wasn't doing much more than copy-pasting info in and out of excel, with some exceptions, it felt like most of the work I was doing could have been automated.
I had two managers, one of them I did not get along with personally, we just did not work well together. The other manager was pleasant and polite and helpful.
My area/team is relatively quiet compared to the rest of the office, so it never really felt like I knew them all very well, but they were always polite and kind to me, and overall I would say the culture is pretty relaxed and friendly.
Express your intent to actively learn, and take advantage of the social events.