[Ria P]

Hello and welcome!

There are just a few things i'd like to add.

A hamster's poops shouldn't be smelly, green or runny. If it continues i'd get her checked out by a vet.
One of my hamsters had the same problem and the vet diagnosed internal parasites which were easily treated.

It could be that your hamster had been fed too much fresh food like lettuce, kale and other leafy greens which can upset their sensitive digestive system.

Why does your hamster have a large rock under her bedding? Many hamsters like to burrow and a rock would get in the way of making a tunnel. What they do need is plenty of paper based substrate.

Are the pebbles big enough not to get pouched? I find flat pebbles very useful under a water bottle or used as a step.

Is her bin cage ventilated with a meshed lid? Lack of ventilation can also make a bin cage smell quicker.

Don't worry if you don't get everything right at the beginning. Nobody does and we all learn as we go.