In general, the SOP for performing an online upgrade which is described at

Procedure is to first disable or in this case chose to uninstall all unnecessary repositories first. The necessary repositories are the OSS and OSS update repos, optionally should not be too risky to include the Non-OSS and its Non-OSS update repos.

Depending on the situation, convert the existing repos to the version of openSUSE you want to upgrade to... If you're performing a re-installation rather an upgrade from another openSUSE version, the repos should already be named correctly. A sed command in the above SDB can help you modify repo names if necessary.

Then, do your "zypper dup" to execute the upgrade/repair/re-installation.
If you're queasy about doing this step which can be hard to undo, you can also download all packages beforehand (as described above) when your Internet connection is unreliable or do a test run.

Reboot and see what your results are.
Again, refer to the SDB link for full details.

If successful, then you can choose to re-enable repositories (don't forget to make sure that each are for the proper openSUSE version) and "dup" again (because this is TW) to update applications and components from those repos as well.