Hi everyone...

Need some advice please: I currently ride on a custom built Cannondale CAAD10 with Shimano 105 componenets. I've realized that 10 gears is not enough for me, as I find myself often times over-paddling going downhill (as in missing another gear to up shift to). I *assume* (?) that replacing the cassette with an 11-speed one, would help things out? I guess I just don't know if the additional gear is for the lower end of things or higher (or rather compensates for both)?

Also, if an 11-speed setup is recommended, what would be a decently priced set? Would the "105 HG (11-Speed)" fit?

I'm really clueless when it comes to the 'mechanics' and technical part of my bike

Thank you in advance