Why are people bothered about achievements? Just curious. I, for one, gets put off by the achievement notifications. Is it mostly to do with 100% completion?

I like how difficult the game is in the beginning, I feel it sends a strong message to the player. And I also like the fact that there are various opinions as to who is the most challenging foe in Chapter I. For me it would have to be Letho by far - you described him very well. Once I learned his moves/patterns, it was just a thing of synchronisation. He is a bit on the OP side, arguably more than the Kayran (which, I have to say, is my least favourite fight in the entire series). I won't spoil it, but you are in for an interesting story.
Geralt's progression from this point on (Chapter II) will be evident and the combat more enjoyable.
Ah, do be thorough in your exploration, it is possible at one point you will meet a very interesting character. Be prepared is all I can say.
The Witcher 2 is one of the games that will give you a proper beating if you are not planning beforehand. I think it has an unforgiving, unique world, a solid story, enjoyable quests, interesting characters driven by believable reasons.
Not my favourite entry in the series, but in certain aspects it tops Wild Hunt. I recall only one moment of genuine relaxation throughout the second game, it speaks volumes about its overall tone. Grim and dangerous, but such a memorable experience. Definitely recommended.
Have fun!
Before I forget, are you going for a Swordsmanship or Magic build?

yes

You are asking the generations who judge life by likes on YouTube or fb why “achievements” are necessary?

Yes, I do quite like a challenge and I appreciate the increased difficulty. I also agree that the tone of the game is good - 'grim and dangerous is right'. With many of the 'rank and file' enemies being genuinely dangerous, it makes exploring the forest in chapter 1 and the gullies in chapter 2 feel quite intense, which I like as well.

Although, I felt that the difficulty in the first chapter was a bit 'hit and miss'. As another example: in the abandoned hospital, I found getting through the specters to be quite hard, but then the Nilfgaardian ghost was a complete joke. Geralt could have literally danced about with his pants down in that fight and never would have gotten hit. The arachas was also disappointingly easy. You can pretty much sit back, light up a cigarette and let Zoltan take it out for you (ok, perhaps I'm exaggerating a little).

At the end of the first chapter I was thinking "eh, this is pretty much a 3-star game". Although, my opinion of it is improving now I'm getting into chapter 2. They story and characters seem to be getting a lot more interesting, and the combat less frustrating.

Thanks for the tip about exploring in C2, I have been trying to do that and it seems there are a good few places to explore, which is nice (the area design seems better than C1 as well). In terms of development, I'm ignoring magic and splitting my points roughly evenly between swordsmanship and alchemy. I also took Roche's path at the branching point in C1.

Another of my (quite many) criticisms of the game is how much more powerful bombs and traps seem to be, compared to Geralt's sword. I mean, I get that they are 1-use items, but the sword is supposed to be Geralt's primary weapon (I see him as a swordsman, rather than a bomber/trapper). Also, using the sword involves going in close to enemies, which entails much more risk of taking damaging blows, so imo the sword is quite under-powered and yet another questionable balance decision. One of the alchemy skill-ups also doubles the (already high) damage of the bombs and traps, which is insane. There is nothing comparable to that for the sword (that I saw).

Gear will get considerably better once you go further into the game, as expected.
The encounter I was referencing takes place at a later stage (although not essential to the story it is well worth the effort
) - for this to happen, exploration is essential in Chapter II. Take your time in Lormark, you will find some great stories and decent items. I'd say this is main body of the game, the most expansive area (but not the best to my eyes). I also sided with Roche (for several reasons) and I can say I do not regret the choice, despite the fact that some players describe Iorveth's path as more entertaining.
I was satisfied with the swordplay overall and I appreciated the alternatives (bombs and traps). My build was focused on Magic almost entirely. And although I was wielding some good swords and excellent armor towards the end of the game, using signs was my go-to tactic.

The abandoned hospital is one of those places I dread visiting because of the specters, not so much because of the ghost. The story there is one of the high points of TW2, imo.

Since the name was brought up in the OP, have you completed Anezka's quest? The forest around Flotsam and Lobinden is my second favourite area overall.
On a hilarious note, if you draw your sword in Lobinden near the guards or workers, they will start panicking. I thought it was a nice touch.

thats you , i like achievements

One thing I don't know, is how to find my way around Vergen.

I think in this case it's less about liking achievements, and more about the difference in what is offered.
Especially because a competitor offers achievements for Witcher 2, when even the affiliate(?) store/client of the actual literal devs of the game don't offer it.

Having said that I'm not sure if the other series have achievements. Not that it would help GOG's case if none of the other games have them.

For those having trouble with combat in Witcher 2, there is "Full Combat Rebalance 2": https://www.nexusmods.com/witcher2/mods/822

IMO an awesome mod by Witcher dev Andrzej "Flash" Kwiatkowski. It makes the combat more fluid and less clunky.

I really struggled at first even on easy difficulty and it simply was no fun. With FCR2 I completed the game on hard twice and had a blast.

Thanks for sharing. The Witcher 2 is designed for replayability but the combat system (and those boss fights in Chapter 1) puts me off. This might make me go back and finally play Iorveth's path.

I actually liked Iorveth's path a bit better. The story is more dramatic and intense with Roche, but Iorveth somehow has the cooler characters and places. Well - the difference isn't that big, in the end it's a matter of taste I guess.

FCR2 combat is a lot like Witcher 3, with dance-like evasion instead of the weird "let's roll" all the time. It really feels like Witcher sword art as described in the books.

That sounds like a really interesting mod. Makes me wish I'd known about it before I started my playthrough!

Well, downside is, you have to start over. It changes so much, vanilla save games are not compatible.