You’re trapped.
Use the door to find it locked. Use the half open box on the right to get the KEY out. Use the key on the door to step outside. Use the elevator button call the elevator and when it arrives use the elevator to step in and go to the ground floor. Walk to the south to find the exit. But it’s guarded by a big man.
Look at the billboard and look at the man to see what’s on offer. Pay extra attention when looking at the ad for the accoustic guitar. Then talk to the guard. Ask him to let you out and if he doesn’t, stay kind to him. He’ll then agree to let you out if you can tell him his name. Tell him you know it and he’ll give a list of options.
Tell him his name is Bobby and it doesn’t really matter how you knew that. You’re free to go. Use the door to leave.
Game source: A copy of the game was found here on the internet.