Air carrier First Officer reported multiple system failures in flight. Flight crew landed uneventfully.

Narrative

Initially we [requested priority handling] for the green system hydraulic indication dropping. Then various failures started like Autopilot One failure at about FL200. On final approach Cabin Pressure amber ECAM appeared with the outflow valve closing; descending through 4000 or 3000. Then through about 1500 ft; the thrust levers not set" message continually kept flashing with the aural warning ringing every time. The Captain kept trying to set Maintenance Control per the message but it would just spool the engines up without setting the automatic function. Even though he disconnected the auto-thrust the message would briefly appear and disappear any way all the way to touch down. After landing the emergency personnel verified the aircraft was clear of abnormalities and we taxied to the gate normally. The after landing flow was accomplished nearing the gate so the slats not fully retracting after shut could have been because both engines were already shut down; but the message appeared in amber."