Hello, Tatiana!
Sorry for a late reply.
On your images node “Custom preview” is on disabled preview mode. Take a look on the screenshots:
1) surface node and custom preview are both on enabled preview mode (both nodes are light gray):
2) surface node is on enabled preview mode (light gray), custom preview node is on disabled preview mode (dark gray):
3) opposite to 2)
In order to hide geometry, produced by some node, click on the node with mouse wheel and then on “Disable Preview” (same for show the geometry – “Enable Preview”).
Hope it’ll help.