Help? Beginner

First day using sketch up pro 2020 and I have all these lines round a room box I have done?
Can any advice why I have them in the background? They do disappear when I orbit the room to gravity view

Can you export a 2D grafic or make a printscreen?
I might help us understand your problem.

It looks like you have transformed one of your walls and your floor.
Can you select a different view.
Then go to file, select export, select 2D grafic, safe the image on your computer.
Then drag and drop the image.

It looks like a graphics card issue. Can you share that .skp file just to make sure there’s nothing wrong with your file.

Try updating your graphics card drivers. Can you fill out your profile so we can see which card you have please.

Read this discussion:

Your a star!!! Thank you!!

To be clear, can you confirm that you turned use fast feedback on? The linked topic suggests to turn it off, and I think that isn’t your case.