The appartement is efficient !
Not very sexy, but it's Berlin ;)
You have all you need for a basic stay, and you are not far of public transport and some night shop and supermarket (good thing to begining or finish a tourist day or a crazy night).
For us, a group of 5 old friends, the unique room was funny and very sweet in the morning. But you have to take that in consideration if you need more intimity.
About Alex > a very good host. We not meet him, but he was very reactive and very helpfull.
Thanks for all :)