Hi, is it possible for a hero with the acrobat skill to take something (treasure, potion,...) or activate a gliph, if a monster stands on it?

Yes and yes. The only thing you may not do when on the same space as another monster is open a chest.

(or attack, but that's clearly stated anyway)

Thanks.

What about the monster movement ,if the overlord must move a monster standing on a gliph when the gliph is activated?OL move the monster 1 space? What if there are no free space and the monster can't move?

Sharaazad said:

The monster must move on its next turn (not immediately), if it can. If it cannot move for any reason, then it does not have to.

FAQ pg6
Q: Can a monster end its movement on or be spawned on to a glyph of transport?
A: Monsters can end their movement on or be spawned on to unactivated glyphs, but cannot end their movement on or be spawned on to activated glyphs. If a monster is on an activated glyph, the overlord must move it off the glyph on his next turn, if possible . Monsters can always move through or attack into spaces containing glyphs