I would make sure to keep those apart at first. Once both of them seem to be working properly, try adding them together and see if there are any issues.
Please note: From the video, this does seem like a very complex system. It’s very hard to re-create something of high quality within a short amount of time. Instead of always comparing your results with this one video, try comparing them to multiple other games with a similar movement/gun system and see if you like the general idea of your script.
I have actually tried doing this before and it failed so badly, I have so much trouble creating these complex systems. Should I possibly try to do something more simpler and come back onto this after gaining more experience and skill?