You are using the wrong software, as the basic concept of Lightroom CC on all platforms is based on syncing everything to the cloud.
If you want do have an offline Workflow, you need to use Lightroom Classic CC *. If you want to have control what is synced to the cloud, you can also connect one Lightroom Classic Catalogue to Lightroom CC and sync specific collections, with the following caveats when importing into Classic:
- Only smart previews, not full-size photos are synced
- No keyword syncing
- No syncings of color marks (as Lightroom CC doesn't have them)
If you import your pictures to Lightroom CC (e. g. on a mobile), the full-size picture is synced back to your Desktop Lightroom Classic. Edits are synced both ways.
* This application was called Lightroom CC some time ago, but Adobe decided to rename it as they launched the new cloud based ecosystem that evolved from Lightroom Mobile and is now called Lightroom CC - much to the confusion of everyone.