Reading a couple of pages of the full complaint, starting from page 15 is surprisingly accessible (assuming German is accessible at all to the reader).

They claim Telekom keeps their transit access points intentionally underdimensioned. In order to be reachable at decent speed by Telekom customers, internet services need a direct, paid contract with Telekom.

Edit: The section numbering is weird. Why does 2.2.0 come after 2.3? On my phone, don't have a good overview.