This article is devoted to the study of derivations in group algebras. Ideals of inner and quasi-inner derivations are constructed, which makes it possible to study the algebras of outer and quasi-outer derivations. We establish a relationship between derivations and characters on the groupoid of the adjoint action. Moreover, we study a connection between the structure of algebras and the number of ends of the conjugacy diagram and, as a consequence, the number of ends of the original group. The results obtained make it possible in the final analysis to give estimates for the dimension of the algebras of outer and quasi-outer derivations using only the combinatorial properties of the group. It is also possible to obtain information about the Hochschild one-cohomology.