what lamp "ceiling" support to use having only a plain 5cm diameter hole
Put a fisher (6mm is enough for a lamp fixture) with a hook next and hang the fixture to it. When you'll move out, just fill the holes with stucco, I assume you live in a 'brick and mortar' house and not in a 'US-style' "wood and glue" home.   

Fisher: 

Stucco: