I know nothing about the finer parts of electronic keyboards, but if the keys aren't weighted you're wasting your time.
This.
Don't get anything without weighted keys.
Do not get anything with less than 88 keys.
If you don't lose interest because you actually aren't interested in playing or learning music you like, you
will lose interest very quickly when you realize your keyboard cannot replicate a real piano to any degree. You won't be able to know this until you find yourself needing to play notes lower or higher than you're able to, because that's not what the equivalent of a toy or a big synthesizer is built for. This won't even occur to you until you want to play more quietly or loudly, and you have to stop in the middle of the song and reach over to the goddamn volume dial and turn it down or up.
It is not good for any kind of complicated music and if you
actually mean to get into playing this instrument in an enjoyable manner, I suggest you actually fork out the €500 and take a look at
Yamaha's most affordable digital piano for the moment. You're better off with a years'-long investment instead of buying something that'll sit in the corner of your room until you sell it for cash or give it to a relative for some birthday present.
It's either that or save up money for a real, acoustic piano, because piano may be a compatible instrument, but you will waste money and completely stunt your progress until you buy something better if you pick a low-quality product. You also risk wasting money if you buy something used anyway - there's often restricted or no warranty, so you're stuck with any damages you receive.