I got the summon scroll from the cave in the jungle and now I am stuck. I'm in human form, so I can use the lizard tunnel to escape, I can jump back to the bridge, I just can't jump far enough, I always end up eaten by the fish in the river. And yes, I found the passage behind the statie, but the thing block the passage, can't sneak around it or jump over. What can I do or am I stuck?

That one's a pain in the arse, yes. There's actually a secret wall tile somewhere near that pillar that you can't pass.
If you click it it'll open and reveal a lever. The lever removes the statue.

Thanks for the reply, I can't seem to be able to find the switch. But I've restarted my game since I've missed a lots in the museum.

For the future:
The tile is on your left (Luther's eye sight height) just as you enter that altar area, before the first two statues.
There's an obvious 'square', since even though the texture is the same as the surrounding wall, it's not aligned properly.