How long before a flight should I arrive?

I have a flight from Manchester airport to Munich, and then to Incheon (South Korea). The typical time to arrive before a short flight is 2 hours, whereas a long-haul flight is normally 3 hours before. My question is although my first flight is to Munich, would I still have to arrive 3 hours before as the connection flight is classed as, 'long-haul'? Or is arriving 2 hours before okay? Sorry if this seems like a stupid question, I'm new to travelling alone and as travelling times to the airport would either allow me to get there 4 hours before the flight or 2 hours before, I would like to know if the latter choice is still safe for this kind of flight?

I have never heard of anyone arriving three hours before their flight.

If you arrive two hours before, you will be completely fine.

4 hours if Muslims 2 hours for everyone else

2 hrs

The issue with when to arrive has to do with how many passengers have to be checked in and loaded on the plane. International flights are in bigger planes with more passengers. You're checking in for an EU flight, so the plane won't be that big. 2 hrs should be plenty of time.

Arrive when you arrive.
The line will be what it is.
It is recommended at LEAST 2 hours before departure.

Is there some reason in particular you are aiming to be last person on board?

Can you guarantee your arrival at two hours before?
Can you guarantee there will be no issues that might cause an extra wait the day you fly?
As you have an option to go just a little earlier suggest you do it.
You can use the time to relax before your adventure. As opposed to fretting will I make it on board at the last second.

Let's look at your two options, and see which sounds better to you.

Option 1 - Arriving 4 hours early, getting checked in, through Security and grabbing a bite to eat before your board your flight.
Option 2 - Arriving 2 hours early, checking-in, and arriving at the gate to watch your plane push back and take off without you.

Now, if you get there 2 hours before will that defiantly happen, NO, in fact the odds are you will be just fine. But what happens if your transportation to the airport gets you there 30 minutes late due to some other circumstances beyond your control. That now only gives you 90 minutes. Or worse what if you are an hour late? Planning to arrive isn't always just about getting to the plane once you are at the airport, it is very often just getting TO the airport.

2hours maybe ok for a domestic flight, but in busy times, and we don't know when you are travelling, the whole airport process can take way longer than expected, longer queues at checkin, even to just drop bags, longer queues at security, people still can get the hang of removing laptop and iPads etc, liquids, you name it.

I would give yourself 3 hours for your Munich flight, this gives you the flexibility of delays getting to the airport, and unexpected delays after you arrive.