@Lietus 

What is the firmware build you are running?

Did you just get the router or was it installed at your previous place? If you have had it before what speeds were you getting then?

Since having the issues have you factory defaulted the router, left the settings alone and tested the speed?

@Tony firmware build: 2.0.2 Build 20180118 rel.38979 (EU)

I just got the router and installed it today, at first had factory settings thats why I tried with different to see if it was fixed, though it wasn't.

I plugged in my 1gbps internet to old router and then routed to the new one just for testing right now and it doesn't even reach the 1/5th of what comes in to the old router when I'm using the old router vs new router speeds, even when using wired lan this scheme: 'old router -> lan cable to new router -> new router -> lan cable to my pc' and speeds are again less than 1/5th of what actually is tested in this method while connecting to old router WIRELESSLY. I did this test just to see what kind of an issue could this be and it confirms something is wrong with AC1200, my old router is some kind of a huawei router provided with a different ISP few years ago.

edit: Also I should mention that something weird with signal strenght is going on as well, every step i take away from the router (from standing next to it) I drop about 10% of my speed, 5g barely reachers 100mbps and 2.4ghz ~70mbps and it starts dropping really quick through both.