thanks everybody. one of the bricks did pop loose in one corner, but it's not going to go anywhere so i'll leave it for now. did a small fire last night for about an hour before going to bed and am slowly burning away today. that is when i heard the pop. overall it is looking good, though. this older design had rocks instead of brick that were loose in some places. plus a lot of old whatever cement had crumbled away. this oven grew up in the old east germany after the second war, and during these times, good raw materials were scarce, so i don't know what was used to repair it, but it has held up until now. so with the new bricks, covering the old cement with new fire cement and sealing the firebox (was really drafty before) a good cleaning above, and gasketing the door and cookplate, this oven burns a lot hotter with less fuel. plus there was no issue with my damper, the stove pipe was half-full with soot!
i apologize for the lack of quality of the first pic.