u/Fit-Resolution4311

Hi, I am Senior DevOps Engineer, 27 Male, and I live in Munich, Germany.
Now that I've saved up my Emergency-Fund (about 12k - 6 months full budgeting of me and my Girlfriend), I have a satellite budget around 1200 - 1400 Euros per month that I can invest.
I'm not asking for anything short term, also I don't wanna use the money from my investments when I'm 40. I'm looking for any suggestions which can be persistent for decades but also I can see the results already after 3-4 years (possibly withdraw piece of it for good) as I'm planning to get out of Germany in that era.
What I was looking into was ETFs, let me know if I'm on right track.
Thank you in-advance.