Hey dude, nice pics, never thought about taking pictures of fireworks, focusing on time must be hell 
Thanks!
Focusing wasn’t all that difficult, just put it to a high f-stop and manually focus to where most fireworks are launched. And with a 30 second exposure time you just have to trigger it every now and then. At the end you only have to filter out the bad shots and crop & edit the good ones. (I also recommend putting on some filter to make the image darker, else the fireworks overexpose and are just white lines.)