Moving content between existing layers

[willip4]

(03-31-2018, 09:50 AM)Espermaschine Wrote: make a selection, copy, paste

Thanks for the prompt response.  When you say make a selection - how do I do this?
When you say paste - how do I paste onto an existing layer?

I attach a screen shot of my gimp image

I want to move the black lines from layer 2 to 1

I also want to move content from 1 to layer 2.