Temperature issue, I hav an h100i pro and it really not enough I think. Also im not trying to over clock till in the future.
Ok, now we're getting somewhere. What kind of temps are you seeing?
In idle between 30 and 40. Ig I say that’s bad because I upgraded from a i5-9600K and maybe I’m not used to that kind of temperatures
Idle temps generally don't mean too much, however a 9900K being around 30C is in no way a big deal. Surfing the web, replying to you, etc my 9700K is 'idle' around 35C (OC'd at 5.0Ghz with a bunch of browser windows going), under a Dark Rock 4 heatsink and fan.
If your temps are not getting near 80C-90C under load, you should be just fine.
The CPU is designed to work up to 95-100C before it beings to throttle. Obviously you don't want this, nor do you want your daily operating temps to be that high, so 30-40C, is really nothing, and your 280mm AIO isn't flexing any muscles to achieve those temps (most likely -if there is no thermal paste, it might be working harder than expected to maintain those temps).
Yh like I said before I’m not a genius in temperature especially in the i9-9900K since it’s a new cpu for me
No problem, we're trying to help. =)
Keep an eye on your temps for sure, if you want to see what your CPU is like under load, you could monitor temps while running Cinebench (for a short test), or RealBench (for a longer test).
I'd recommend using something like HWINFO, or even CORE TEMP to see what your CPU is up to, though RealBench sorta tells you while it's running.