We will talk about a combinatorial method for studying derivations on bimodules that arise as a completion of a group ring with respect to various norms. It will be shown that for a wide class of norms all derivations are quasi-inner. The question of the coincidence of quasi-inner and inner derivations depending on the internal structure of the group will also be studied. The work is a development of the results obtained jointly with Prof. A.S. Mishchenko and Prof. A.I. Shtern