How to fix a slow connection?

Question

Mikrotik

There are two buildings at a distance of 600 m. In each local network 10.10.10.0, IP for all computers are registered manually. They threw out the optics, at the ends there are microtics with an sfp port. In the settings of the first microt, PPPoE is clogged, in both bridges on the involved ethernet and sfp. The network and the Internet in the second building are very slow, what can interfere?

Answer 1

Mikrotik has a speed test, first check the speed between Mikrotik
tools - bandwidth test
PS: 2 rings interfered with me (at work), somehow I found them.

Answer 2

Thanks to everyone for the recommendations, it was still in the network cable to one of the computers in the second building. Replaced, the network and the Internet fly)

Answer 3

If there is a ring, then the CPU should be loaded at 100% on the Mikrotik.
Try cleaning the optics. And show the config (export), it is not known what bridges you configured there)

Answer 4

I advise you to disconnect everything from the second Mikrotik, except for communication with the first. Physically.
and test the connection.
Try replacing the optical patch cord with a new one. They are cheap now.
Make sure that you are using the correct patch cords)) single-mode / multi-mode depending on the optics.
When they accepted work on optics - did you have a test?