Is it still worthwhile to buy a Ps4?
Depends on whether you are more of a casual player or an extreme player
I would like to play some games already
Well, that depends on whether you can wait a little over a year for the PS5 or not. Since the PS5 will be backwards compatible with PS4 games, you can play all your PS4 games on the PS5. Meaning, you could now buy a (possibly used and therefore cheap) PS4 or PS4 Pro and then stock up on many PS4 titles. The decision is up to you.
PS: What do you mean by "another one"? Is your current one broken?
With "one more" I mean if it is still worth the middle of 2019 to buy a Ps4. A good buddy offers me his Ps4 for 130 euro how do you like the price?
Yes, it is well worth it.
Well worth it, if you've never played ps4, there's certainly a lot of gambling for you. In addition, she has now become much cheaper. Sure the ps5 should be backwards compatible, but to what extent this will all be so you can think I do not say exactly and the question is whether you can just insert the old discs there. In addition, it will probably come sometime in 2020 and will therefore be expensive to start first. In addition, you can buy great used games at great prices for the ps4 on eg rebuy or eBay etc.
Depends on how the PS4 is still in action!