The problem is that you are not connecting. You are on separate itineraries. As far as LOT is concerned you are someone who is checking in for their flight at TXL - you are NOT a transfer passenger. LOT's check-in deadline, according to their web site, is 60 minutes.

I suggest you contact LOT and get them to put a note in your booking to say something like "Arriving on CO-whatever at 0750 with hand baggage only". This may persuade them to keep the flight open past the normal check-in time.

It's a long time since I last used TXL - but am I correct in thinking that TXL has no airside as such, but that you check in at a desk right next to the gate? I was at HAJ last week, which has the same system - and I noticed that people were checking in for my flight long after the 60 minute deadline, right up until the time we boarded.

So - I'd say you're in with a chance, but it's going to be tight and you might not make it.