2 ethernet connections between two Switches

If the second switch is unmanaged, then you're in for a world of pain. Without management features like Spanning Tree Protocol (STP), then you'll probably create some kind of loop, and that will invariably, eventually lead to a broadcast storm.

This is why if you're connecting switches together, especially to improve interconnect speed, then you need to configure LACP on both switches, so that they see it as a trunk path between the two.

I'm willing to wager that by connecting the two switches together in a naive way, then you'll either reduce network performance by encouraging routing loops, or cause broadcast storms which will bugger both switches equally.

Sell the unmanaged one, get an identical one to the first, and do it properly.