Good communication is a key skill for a project manager.
Good design of the product is assumed by the client. The key to keeping things running smoothly and making the client happy is keeping them informed.
Give the client regular updates, even if there is nothing to tell them. Ask the client for feedback. Are they happy with the way the project is going, your communication with them, the deliverables, etc. If something is running late, tell the client and the reasons. Don’t assume they know it will be late or why it will be late. Often just telling them will satisfy them, instead of the client contacting you to say your deliverable is late.