Failed upgrade from mavericks to High Sierra

Look in your Applications folder for Install macOS High Sierra.app, check that it is 5.21Gbs, that will indicate it has downloaded fully, if so make a copy of it and move it to an external drive or USB stick for safe keeping. The reason for doing this is that the one in your Applications folder will get deleted upon a successful installation. Having a copy means you don't need to go through the whole turgid download experience if you need to reinstall or want to put it on another Mac.

If it is anything less than 5.21Gbs then it has not downloaded fully, so move it to the Trash delete it and start the download again.

As you are moving from Mavericks to High Sierra, there have been quite a few changes, so have you checked that any third party apps you have can run in High Sierra or if they have updates that will allow them to do so. also you will need to check with manufacturers of any printers, scanners etc to see if they have updated drivers and software so they will run in High Sierra.