How is it unbalanced? Just that the graphics card is old and everything else is new?
"Unbalanced" depends on your workload, but for gaming a 9900k is complete overkill unless you're going for high-end graphics as well - you'd get indistinguishable performance with a CPU $200 cheaper than that. Then again, it might be that you're using the CPU for something besides gaming? Streaming? Rendering? Video editing? CAD? I kind of hope so, as you've made some rather poor component choices otherwise.
From looking at your system specs, you're using an old 22" monitor - I'm assuming it's 1080p 60Hz? If so, any GPU beyond an RX 570 or 580 is pretty much overkill (or at least quite bad value compared to those two). They won't get you 1080p60 Ultra in AAA titles for years to come, but they're incredibly cheap and perform well. Then again, you might be planning to upgrade the monitor in the near future, in which case a beefier GPU would make sense.
Honestly, though, if gaming is your heaviest load, my plan of action would be to sell the 9900K, get a 9600k or similar CPU, and put the extra money into a better GPU and monitor - either 1080p with a decent refresh rate (and preferably FreeSync/"G-Sync compatible"), or 1440p60. There should be decent options for both of these that aren't overly expensive. Decide the GPU based on your total budget and resolution/refresh rate goal, and whatever you do, wait until the upcoming one-two punch of GPU launches has landed and we have some reviews.
edit: I realized I ought to be a bit clearer on what I think you should do if you indeed have a use for that monster CPU (which of course is the more reasonable assumption here). You say you're unsure which games you'll be playing, and again, it looks like you have a 22" 1080p60 monitor. If that's the case, the value proposition of a (lower) midrange GPU (RX 570 or 580, GTX 1660 or 1660 Ti) is far superior to something like an RTX 2060. The
only reason to go for a GPU that powerful with a monitor like that is future-proofing, if you want to keep the GPU powerful enough to game at 1080p60 for 3-4 years or more. Beyond that, you're just throwing money out the window, as you won't see anything real in return for the extra GPU cost. Of course, going lower down the GPU range also leaves you money to upgrade your monitor, as mentioned above. This is a balancing act - do you go overboard with the GPU with the intention of upgrading your monitor as soon as you can afford to, or do you buy a cheaper GPU that better matches your current monitor, but will be a poorer match for any upgrade on that front? Ultimately you'd have to make that call, but unless you're into future-proofing your hardware, I wouldn't spend more than $2-300 on a GPU for your uses for now, and there are good arguments for going even lower than that. On the other hand, you've built a PC with a $500 CPU, so you're obviously able to scrape together rather significant sums of cash - in which case going for something like an RTX 2060 now and a good monitor to match in a little while could make sense.
(true not /s)
). Or wait a bit, but that is always valid 
