Watching your video back audio it is already quite professional. The next step up would be to invest in XLR microphones and an audio interface that provides enough power (48v) if you plan on getting an XLR condenser. Also as
@RedFox said turning the volume and gain down, then getting closer to the microphone would reduce any background noise however you don't wanna be so close that it picks up your breathing. The Blue Yeti is an excellent all round microphone for decent audio quality so you may not need that extra edge unless your really serious about audio. Saying that you could also invest in a dynamic XLR microphone which doesn't require power (still need an audio interface) compared to a XLR condenser that needs 48v so you don't have to invest in an expensive audio interface with phantom power. Though I have been using this as my go to guide for audacity, your S's do seem to hiss a lot when you speak which could just be your natural way of speaking or you may not be using compressor and hard limiter on audacity (if that will help, may not) since they reduce any noise that goes above a certain decibel.
This is the audacity guide I memorized and use for all audio
I use a cheap £50 microphone, you can see how good audacity can be at audio editing if you watch my gaming news video. Hope this helps somehow.