I feel for you Liaconn, sound is a problem in my apartment as well.
I dont tend to hear my upstairs neighbour just walking most of the time, but occasionally she wears high heels and it is quite literally like someone is hammering - the cast concrete seems to amplify the sound.
We also hear running feet on stairs, it actually sounds so loud that you would think it was a herd of elephants and it might only be one small person.
Anyway, my advice to you would be to engage with the upstairs neighbour. My previous upstairs neighbour had my head done in playing music that was blaring into my place through the ceiling and I approached him and he was super nice, put a cushion under his speakers, and that was the end of it.
It could be as simple a case as the guy upstairs putting down a mat, or not wearing hard soled shoes indoors. As apartment residents we are all aware of noise travelling through the cavity spaces and over hearing each others washing machines, doors slamming, loo's flushing.
Your neighbour sounds like a decent person who was nice about an issue before, so Id just make him aware how loud it is for you and let him make changes himself. Id say he just doesnt know.