As a general recommendation:
for flights within Europe, arrive at least 2 hours before departure
for flights outside Europe, arrive at least 3 hours before departure
If you are travelling with hand luggage only or have already checked in online, you may need less time at the airport. However, always allow extra time for traffic delays, queues at security, or possible disruptions in public transport.
During public holidays, weekends, and school holidays, airports are often busier than usual, so arriving even earlier is a good idea to avoid stress.
For the most accurate and up-to-date advice, always check the website of your departure airport and the airline you are flying with.