When I changed the MTU have been no changes.
When I change the protocol to none, the speed increased.
When I changed the protocol for stp, the rate is the same as in none.
When changing to rstp, internet speed is reduced.

Working!!! Thanks normis and strods for your help!

Problem solving.
1) interface bridge set bridge mtu=1500
2) interface bridge set bridge protocol-mode=none

# jan/05/2017 12:54:54 by RouterOS 6.38 # software id = TTGC-0AJH # /interface bridge add admin-mac=6C:3B:6B:19:AA:D9 auto-mac=no comment=defconf name=bridge /interface ethernet set [ find default-name=ether1 ] advertise=1000M-half,1000M-full name=WAN \ rx-flow-control=auto tx-flow-control=auto set...

No change. Forgot to say that when you connect to the first port and failed to raise the connection with the provider by auto negotiation to 1 gigabit. At the port №2 everything is OK. I can give access to webfig.

Problem. There are new MikroTik hAP AC. The provider gives 1 gigabit Internet. When connected directly to the computer network card speed is 750-800 Mbps when connecting to the router, the speed drops to 250-300 Mbps. (wan2lan).

serial number : 673706A48473
current firmware : 3.34
OS : 6.38