Can anyone tell me what I have to use on the crank to get across the bridge.

There is a handle for it, I think found in a chest.

there is a passage (pretty much at the beginning of the spire-cave) to an upper section of the cave where the tool to activate the crank can be found in a chest.

i could not figure out myself for some time how to get up until i was struck by a piece of luck - or is this game really that sophisticated?

Anyway, while passing this hole in the ceiling for the gazillionth time 2 mountain spiders dropped down from that hole and on top of each other. doing some weird spider-climbing (prepare for a lil bite here and there) got my party to this upper section, but - for crying out loud - how the the smeg are you supposed to get up there in case no spiders drop down

Just out of curiosity I'd fancy an answer to that one as well - good luck