Is possible manage the QOS without knowing the maximum bandwidth available?
For example, if I have a band from 10Mbps to 15Mbps and I want to give priority to
VoIP traffic. If I create 2 queue with different priority without max-bandwith.. works?
I have to set the maximum bandwidth available? but if the bandwidth is dynamic 10 to 15Mbps
what can I do?

It is a very difficult problem. If your upstream device understands DSCP then you can tag outgoing traffic with a mangle rule. This will not control inbound traffic, however.

If it is a wireless link you can enable WMM on both sides and then set the RouterOS priority with a mangle rule.

Otherwise you will need to set the bandwidth in the queue to the lowest it will ever be.

watch out, WMM not working under NETSTREAM , u must set banwith to garanted level.

Suppose to have 10Mbps garanted at the source (point A)

now distribute 10Mbps to other 4 points (points B,C,D,E)

A-->B-->20 Clients
A-->C-->10 Clients
A-->D-->50 Clients
A-->E-->10 Clients

for the big quantity of traffic I put the traffic priority rules
on point B,C,D,E

How to set max-limit on queue tree If the 10Mbps garanted is shared for the other 4 points?

Suppose now that the band is saturated with P2P traffic.
I want that a customer, when launches a speedtest, it will have its highest level of bandwidth.. for example 6Mbps.

how?

This is a feature I'm also missing. I would like to have a priority working on packets without the need to specify the max bandwidth.

The solution might be to determine when a link is congested and dynamically change the max-limit with the maximum capacity of the link.
But I don't know how. Do you have any ideas?