If you get stuck, here are hints and solutions to all the puzzles.
WARNING this contains many spoilers.

This room is linear meaning one puzzle leads to the next.

The red cubes:
1: There are four red square holders on the center bookshelf
2: Can you find four cubes that fit the holders?
Solution: There is 1 red cube hidden in each of the bookshelves. They spell the word OPEN, place them in the red holders

The center coffin:
1: Did you look through the window?
2: There is a key in the windowpane
Solution: the key is to open the center coffin in the keyhole

The gold coin key:
1: The shape of the gold coin key is important
2: look for a gold ring it might fit
Solution: There is a round gold plate on the right pillar on the empty wall place the coin key here

The 3 digit code under the ram:
1: There is a hint in the red box in the cabinet
2: does the round gold plate in the pillar seem familiar?
Solution: Go back and take the gold coin key and place it on the round gold circle plate in the room with the ram lock. The code is now on the closed wall behind you: 666

The throne room:
1: You need to put marbles on each scale. Perhaps the shelf above is a hint
2: The scale has a blue ball end and a gold ball end
Solution: place 3 blue marbles on the left scale and 5 gold marbles on the right scale

The record player room:
1: If only you could use the record player.
2: Have you searched all the drawers?
Solution: Find the record in the drawer in the desk at the end of the room and use it on the record player

The mirror room:
1: Is that a big mirror? But things seem different.
2: The key for the bottom cabinets in the record player room
Solution: Move the hat to the coat rack. Move the sphinx from the chest to bottom center in cabinets. Move the gold coin from the drawer to the table near the mirror. Move the 3 blue statues to center on cabinets left to right; human, bird, jackal. Move the gold jackal from the cabinet to the bookshelf. Move the stone statue to the center left cabinet. Move the black heart to the upper center cabinet. Drag the large red floor vase to stand left of the cabinets

The puzzle in the record player room:
1: Does the shape above the end table remind you of something?
2: The pyramids fit here
Solution: The four pyramids are hidden: no1 in the first room on the bookshelf. no2 in the room with the ram lock. no3 in the secret room that will open if you pull the lever on the throne. no4 on the altar near the big owl. Place them on the table so they have the same height.:

The exit door puzzle:
1: The floor tiles remind in front of the exit door resemble something
2: The objects on the shelf fit on the floor tiles - what could this resemble?
Solution: The tiles are a map of this basement. The objects should be placed as they are in the rooms

Please let me know if you need more hints or still get stuck anywhere.