There's a tool called ADCDownload, which allows you to resume downloads from Apple Developer website. It's a command line tool so you'll need to use the Terminal. However, it may not work, as the tool hasn't been updated in awhile.

As a last resort, you can try to download bittorrent version of Xcode (but there's always a risk of downloading bad files from unknown source and it's very difficult to find Xcode, if it even exists)

You can try to download bittorrent version of Xcode but there's always a risk of downloading files from unknown source and you may not be able to find the latest version, as I could only find Xcode 9.

Side note: In the past, I would've recommended a tool called ADCDownload, which allows you to resume downloads from Apple Developer website. But it hasn't been updated in awhile, and likely no longer working.

You can try to download Xcode from a third party website such as xcodereleases.com and use the browser's download manager to resume downloads, as you have tried before.

However, it might not be possible to resume, as the website might not allow resuming downloads especially if you wait too long before resuming the downloads (as download links could expire).

As a last resort, you can try to download bittorrent version of Xcode (but there's always a risk of downloading bad files from unknown source)

There's a tool called ADCDownload, which allows you to resume downloads from Apple Developer website. It's a command line tool so you'll need to use the Terminal. However, it may not work, as the tool hasn't been updated in awhile.

As a last resort, you can try to download bittorrent version of Xcode (but there's always a risk of downloading bad files from unknown source and it's very difficult to find Xcode, if it even exists)