The lever should open a passage through the cells to the left. Activate it and you should be able to proceed.
If you can't see where you're supposed to go, then please provide a screenshot and I will annotate the way to go for you.
Viewing post in [RPG] GROVE: "Dark Places" (v0.308) comments
This looks to be an issue with the translated build as that 'GateBottom' text is not supposed to appear at all (it's the name of the asset, so it probably got flipped somehow). The gate is working in the current ENG build of the game so I'd suggest you play on the english build for the caves first, then switch back to the RUS build when you're past the gate.
Unfortunately we don't work on translated builds so there isn't much we can do at the moment, but I'll forward this issue to the translation team!
-RegalBuster
*EDIT* - Made a temporary fix but the translations for that map have been removed as a result. Download the newest Russian version, or the English version to get past the area. Thanks!