1. Why sometimes chamber block not working also against tutorial bot?
And if your chamber don't work against long axes you will die by first hit.
-- It could be that your timing is off. It is a somewhat small window to do it. Physically their weapon has to slam into yours as you pull back the weapon to strike, but the timing is basically to attack just after the whiff sound from theirs wing.
2. Why sometimes a guy with 1h sword/sabre can strike 2 times in row, first against my shield and when I try immediately to counterattack with my 1h axe I get his second strike? It's physically not possible to swing two times in a row but it happened to me in game with different people.
3. How is a speed of weapon works in combat, f.Ex. sabre 101 and axe 96, can I strike twice with sabre or will sabre simply first reach the target?
--When you have a shield you have a 30% speed penalty so you will swing a lot slower. The main thing might be where a person is standing. You have to make sure that you try to hit them in the early part of your swing. So if you counter attack with a right swing, make sure you have the guy over your right shoulder so you hit them on that part of the swing. Also you really have to counter immediately, even a slight hesitation and fast weapon can still beat you. So again, good position to hit them, and a fast reaction, and you should be able to connect.
4. 2h weapon make lighter 1h stunned, but if I use the shield, can I strike back or make 2h weapon also stunned a guy with shield? If I have a long axe/berdiche… and always hold a mouse
--Hrmm not sure here actually how stun translates onto the shield. I think you should be ok to retaliate but don't quote me on that

if you are left clicking and the sword doesn't come back to strike immediately is how you can tell if you are stunned. But I think for the most part that with a shield there is minimal stun.