This will make a nice coop. If you can,,, install ventilation in area I marked with RED. Do same on opposite back wall. . Install a closable window where I drew in BLUE. Install window of size that suits you. Bigger provides more light, and ventilation in summer. I would leave door as is.
Do not change roof,,, since not necessary. Make your roosts inside at half the height of the structure. This way the ventilation (year-round) will be well above chickens' heads. The window should be opened ventilation during warm weather. Needs to be secured with hardware cloth to protect from predators entering. The closed position should let in daylight year round.
Also do install a small pop door on bottom. About 6 inches above floor is ideal. Inside litter gets contained inside. You can choose an automatic pop door if you so desire. This lets out your chickens at the "crack, of dawn"
Ask anything else you are not sure of. Plenty of knowledgeable peeps here on BYC.. Did I also mention FRIENDLY
WISHING YOU BEST,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,and