Question Awful performance on a new build

[SneakyChippy]

After spending about 900 euros on new components to upgrade my 4 year old rig, I was met with a shitty surprise when i benchmarked my system & also the new CPU seems to be working harder than it should. Also opening tabs is a bit laggy & dragging anything around the desktop lags as if my CPU is from 2010. How the f**k is this possible ? It did however give me a better FPS rating on BF5, so i have no idea what's going on. It does feel like it has something to do with the CPU, but i have no idea. Any idea how i can fix this ?
I'm desperate :/

Old rig:
CPU: intel i7 4790k
RAM: DDR3 1600mHz Corsair Vengence (2x8, 16gb total) (old af)
Motherboard: Asus Z97-A
GPU: GTX 1080 ti MSI Gaming X

New rig:
CPU: intel i7 9700k
RAM: DDR4 3200 mHz Corsair Vengence (2x16, 32 gb total)
Motherboard: MSI MPG Z390 GAMING EDGE AC
GPU: GTX 1080 ti MSI Gaming X
(I kept the same GPU)

UNIGINE Valley Benchmark results;
Old rig: 90,3 average FPS
New rig: 87,9 average FPS
Benchmark settings: Ultra quality (everything set on absolut max)
Resolution: 2560×1440p

Now how on earth could i possibly be getting LOWER benchmark results & generally bad performance from my new rig (compared to my old rig) ? Do i need to download some special drivers? Do i need to change something in my BIOS ?

 

[rgd1101]

fresh os install?
cpu temp during benchmark?
make and model of the psu?