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There's a demo available, try it first, then decide. That's why I bought it.

Well, the second game is an improvement to be sure, but it's still the same core gameplay, just refined. Narrative wise it's much better and the linear areas are sometimes replaced by bigger environments which you spend a lot more time in. The camera and controls are similar, the wide screen can be disabled. It's still stealth based, shooting is discouraged and you don't really get that many weapons at first anyway. If stealth gameplay bores you I don't think the game will be to your liking.

Yes, because TEW2 is very different. It is an open-world game with enemies that randomly wander the world yet forget about your existence in 20 meters, houses that are mostly empty but give you infinite crafting items, completely circumventing the ammo capacity as you can just magically create ammo from gunpowder anywhere. It is closer being a Division: Halloween Spooky Edition that the original Evil Within. The only place you can see the old game is the boss design and the quasi-gimmicky combat against them. (Although the bosses are even crazier, so TEW2 got that one quite right.)
Oh, also, it really wants you to sneak. If you alert an enemy, that somehow magically alerts everyone in the entire game world to your presence. Makes a few particular mandatory routes… interesting and ending up something akin to a Benny Hill chase scene.

Should I buy the evil within 2 if I did not like the first one?

You're clearly interested in it so why not? In the best case you'll love it and in the worst you'll hate it. It'll probably be something inbetween. And considering the game goes for like 8€ you might as well go for it and take it for a spin.

If you did not like the 1st, you are very unlikely to like the 2nd.

Its bad, the open world doesnt work well, often exposing the terrible AI
The bosses are a joke.
inconsistent, easily exploitable, small sections that incorporate different genres on a much much smaller scale,
that kidman cover shooter section...why, just why?
Btw, all enemies die with 1 to 3 stealth attacks.