what are the level brackets? i thought it was every 4 levels but now im not sure ^^

I believe they are:

1-4, 4-7, 5-9, 10-20.

oh wow 10-20 sucks, was wondering why people seemed alot stronger than me

How's that?

I'm sure about the 1-4. 4-7 is wrong, at 4 you won't see any level 7 equipment on enemy. It may be more like 5-7 or 5-10.
At level 7 you'll face level 10 (at least). I've been afflicted by my first plague at that level.

Nope, 4-7 is correct. If you're level 4 in a group with a level 5, you can get into king of the hill matches.
Actually sometimes just being level 4 solo or grouped with other level 4s you can get into this 4-7 king of the hill match.

Not talking about grouping, while playing alone as a level 4 I didn't see any kind of L7 equipment. And believe me I stayed at 4 for some time. However as soon as I dinged 5, I started seeing all kind of shiny stuff and new skills. Hence my conclusion 1-4 and 5-10.

I did play some king of the hill matches at that level, but they weren't any L7 only lowbie.

back in my noobdays at russian server, match brackets where set up to 2x your level but not more then 10lvl difference
I mean if you are level 4 the max level in your fight could be 8
If you are level 6 max level in your fight 12
If you are 13level max for your fight was 23
but es changed since then and idk how it is now