A walkthrough for Gym Escape
Take dumbbell rod, notice key on treadmill
Click right of the heavy bag, where the cables are to zoom in. Click dark cable to see a switch, turn it. Now you can take the key from the treadmill. Zoom out and turn right
Open right cupboard with key, take cable and knife.
Take circular saw, click on it in your inventory and attach the cable (at the bottom of it)
Go back left. Use knife on heavy bag to get another key.
Use knife on both upper corners of the black poster to see another switch, use it
Zoom out and click on the rests of the poster to zoom in. Put the saw next to the treadmill and plug it in
Zoom out and click the fencing. Use the saw on all four sides. Destroy the mirror with the rod. In the lower left corner you find a handle.
Go back right and open left cupboard with key. Take the metal rod. Use it with the handle (hardest part of the game!) to make a screwdriver
Zoom on the bike. Click it under the saddle to move it. Zoom on the vent, unscrew the screws