The HDMI connection on your 390X can only support a maximum of 4K@30HZ. This is expected behaviour.
If you use the DisplayPort 1.2 connection on your 390X though, coupled with a DP-HDMI 2.0 adapter then you should be able to get 4K@60HZ.
Really appreciate ur reply. Can u please send me a link of any specific model on amazon.com? Or any suggestions because theres a lot of models some are labeled as "active" 4k others are standard
and its not cheap so i dont wana get the wrong one.