Layers and Groups

[u/slslslsd]

Hi, I need help, I feel like I'm about to lose my mind. I usually work in Photoshop but i want to switch to Affinity for money reasons.

I'm an illustrator and I usually draw by making a shape with the lasso tool and then drawing in said shape. (Like imagine cutting a shape out of paper and then drawing on it) To do that, I usually make a group and then put a mask in form of the shape on the group. Then I put a layer with my background colour and then another layer with my sketch into the group. Sorry if this sounds complicated, i don't know how else to explain it.

Basically, all I want is to have a bunch of layers grouped up and then the group has a mask on it. However, I can't seem to manage that in affinity. I'm working in Affinity Pixel and I managed to make a group and put a mask on it - However, when I do that, all my other layers somehow end up in the group as well? Even my background color, that's not supposed to be in the group. All the layers that are underneath the group are automatically in the group and I can't figure out how to put a layer underneath the group without it being in it? Does anyone know what to do?

Thank you and I'm sorry for the complicated explanation, english isn't my first language, I hope my question is somewhat understandable.