I found the following users who may fit your language exchange criteria:

Username	Date	Post Link	Relevance	Offered Matches	Sought Matches
u/haunting_concept_670	2021-01-02	Post	`8`	German, English (C1)	Russian
u/theflydutchman	2020-12-02	Post	`8`	German, English	Russian
u/barzhikev	2021-01-12	Post	`8`	German (C1), English (C2)	Russian
u/teconz	2020-11-29	Post	`8`	German (Native), English	Russian
u/agodcherry	2021-01-12	Post	`8`	German (Native), English (C1)	Russian

Please feel free to comment on the above posts to get in contact with their authors.