Hi, Welcome to OpenStreetMap.

Thanks for adding your new speed data. Unfortunately, it went a bit wrong and you added a new highway atop the existing highway. Your thinking was correct, the existing highway should be split and the new section speed tag amended. I was able to figure out what you wanted to do and made the amendments, (OSM practice is to make corrections to existing features where possible to maintain history). Please check that I've got the position of the 30 limit placed correctly.

Regards Bernard.