I transformed my remaining 1&1 position at EUR 18.54 into shares of United Internet - the parent company of 1&1 - at EUR 24.30.
My main reason was the risk of a squeeze out as described by @Aron here and that an investment in the parent company aligns us better with the interests of the company at large and Dommermuth.
Similarly to 1&1, United Internet is attractively valued and the success of the investment will depend heavily on the new 1&1 network.
If i will find the time i might elaborate further on the decision.
I remain interested as well to increase the position depending on more research and an even better understanding of risks (e.g. Network progress, risks of getting fined by BNetzA for failure to meet coverage obligation etc.)