My only real goal is to retire as early as I can.
That should never be a life goal for a 20 year old....What about your entire life between now and retirement??? That is 40-50 years that you have skipped. You are literally just starting out so don't be wishing it all away just yet.
Your short term goal should be to ensure that your apprenticeship is successful and you become a qualified tradesperson. Simple
Secondly, can you specialize within your trade? Increasing your income early in your career goes a long way to building wealth as long as you can maintain a sensible lifestyle and live within your means as
@SBarrett already said
Thirdly, what do you want to experience in life? Your trade can open up opportunities to work abroad, experience new cultures/climates, all while earning money.
After that, you may not be thinking of it now but where do you want to live, do you want to be married or have kids. None of this is set in stone but building a good pot of savings will give you opportunities in your late 20's/early 30's to buy a home if you are ready to settle down.
I would like to own a house but i at also open to the idea of building a granny flat in my parents house.
A bad idea in my opinion. Do your parents even want that? They might be waiting to kick you out at 21 to reclaim your bedroom

You are far more likely to want to move out/away from your parents in the next few years so a better plan would be to plan for how you could afford renting with friends. How would paying market rent vs paying your current rent impact your savings?
Other than that, create a simple budget and monitor your spending. Figure out how you earned the €5k, was it from a reduction in socializing or was it because you have been working/earning more. When restrictions lift, will you end up spending a lot more? Don't get too obsessed with tracking everything you spend, you need to enjoy your 20's too. And finally, get savvy about what you spend your money on. You can enjoy the same lifestyle but for a lower cost than the average person. A simple example that is probably relevant to you, never buy a locked bill pay phone on 24 month contract. It is hundreds of euros cheaper to buy the same phone unlocked and then go sim only for €10-15/month. There are several things like this that will save you a lot of money without making sacrifices