1.12.2 forge server several ticks behind, super laggy

I got a 1.12.2 server up and running after fixing some issues , the thing is that even for me, the host, the server is several ticks behind, i even had to set the max-tick-time to -1 to be on the server without it crashing. I have good internet and im dedicating 6gb of ram to it, but it still uses 1200mb more or less, here is a picture: https://ibb.co/RbcwgzP

chunks load just fine, its the lag thats unbearable, i cant break blocks, cant walk without teleporting back to where i was, nothing.