Slow write speed and read speed on maximus x apex with G-SKILL-TridentZ -2-x-8GB- DDR4-SDRAM-DDR4-4400

[willem.exist2]

Computer:
maximus x apex
G-SKILL-TridentZ -2-x-8GB- DDR4-SDRAM-DDR4-4400
Corsair H100i V2

I am overclocking to 5Ghz.
Ram timing setup to XMT DDR4 4400.
Ram speed set to DDR4 4000 (4400 does not work) 19 19 19 39 2T

Running Performance test I get:
Memory Mark 2464 : 82% percentile
Memory read cashed: 34866 99% percentile
Memory write 3488 22% percentile
Memory read uncashed 22474 99% percentile
Memory latency 16
Memory Threaded 45476 99% percentile
Database operations 76 67% percentile.

Why are the writes so slow? What can I do to fix this?

 

[willem.exist2]

MERGED QUESTION
Question from willem.exist2 : "Slow write speed and read speed on maximus x apex with G-SKILL-TridentZ -2-x-8GB- DDR4-SDRAM-DDR4-4400"

Computer:
maximus x apex
G-SKILL-TridentZ -2-x-8GB- DDR4-SDRAM-DDR4-4400
Corsair H100i V2

I am overclocking to 4.5Ghz. 29% to keep temperatures down
Ram timing setup to XMT DDR4 4400.
Ram speed set to DDR4 4000 (4400 does not work) 19 19 19 39 2T

Running Performance test I get:
Memory Mark 2464 : 82% percentile
Memory read cashed: 34866 99% percentile
Memory write 3488 22% percentile
Memory read uncashed 22474 99% percentile
Memory latency 16
Memory Threaded 45476 99% percentile
Database operations 76 67% percentile.

Why are the writes so slow? What can I do to fix this?