Hi,
Welcome to Microsoft Community.
Yes, you can use SharePoint offline. Check this official article: Sync SharePoint files and folders (microsoft.com).
Basically, you can sync a specific SharePoint document library to your local drive. However, as you want to use it offline, so make sure you turn on the 'Always keep on this device' option for all needed files before you disconnect the internet, otherwise you will not be able to open files offline.

Another thing I'd like to share with you is that if you make any changes with files in the synced SharePoint folder locally, they won't sync the editions online when you are offline. However, these files will get synced as soon as you connect to the internet. But if anyone also edited the files during the period, you will probably get some warning message saying there have conflicted versions for the files.
Hope this will help and feel free to post back if you need any further suggestions.
Best Regards,
Mia