I think you did an amazing job!!! Your patience and perseverance paid off!!! I have a remote controller but haven't used it yet - still in the box....I tried long exposure shots for my first time too - I posted them a few weeks ago. Mine were way more blurry than yours - you succeeded in getting the background sharp.
Take a look https://steemit.com/photography/@countrygirl/night-time-city-lights - I have a Nikon D3100.