Display Current WordPress Site While Updating Theme

I am currently using WordPress for our company website. I want to update to a new theme and redesign the site. However, I don’t want to take down the current site while I work on updating the new theme.

I already uploaded the new theme to my host and to WordPress. The problem for me is that I need to be able to update and view the files via WordPress as I’m not an experienced programmer. Is this possible?

For example, I want to create a new homepage, but in order to create a new page via WordPress I have to have activated the new theme and choose the homepage template from the right.

Thanks for your help!