2 Yiden come to a Din Toiro. Both speak russian. The claimant speaks Hebrew fluently, the defendandt understands Hebrew, but cannot defend his cause in Hebrew, because he is not fluent enough in spoken Hebrew, but is fluent in German. which the claimant understands a bit, but cannot speak. Dayonim speak German and Hebrew, but no Russian. Basically both claimant and defendant can perfectly communicate with each other and with Dayonim, but would eventually not be able to completely follow the argumentation of their respective counterparts. How should this situation be treated?
The Dayanim of a Beis Din must understand the language in which the two parties present their cases. This does not seem to be a problem in your situation, since the claimant can present his case in Hebrew (which the defendant understands) and the defendant can present his side in German (which the claimant understands).
If each party cannot understand what the other one is saying, there would be no choice but for one of the Dayanim to repeat back to each side his case as he presented it (to ensure that he is correctly representing the words of that party) and then repeat it to the other party in as accurate a translation as possible.
Obviously, Dayanim who speak Russian would be the ideal solution.