Im a RPG/TurnBased veteran but never played any of the shadowrun games. I intend to start on normal difficulty for my first playthru.

To my understanding most favored pc class is a Decker due to the fact that decking unlocks some extra content and the only npc Decker is lame.

1. How should i start a s a Decker charactert?

Human or elf? Drones or Assault Rifles? Do i need to invest in dodge and body? (for normal)

Can i master Assault Riffles, Drones and Decking in one game?

2. I was also considering using decker for my second playthru (on hard diffcoulty) and using something simplier on my first (normal) playthru. Like a Melee Troll!!!

What melee Troll would be more fun to play:

Unarmed or weapons? Chi casting or throwing?

Is it any fun to play melee/throwing troll with no chi casting? (just implants and stuff)

3. On both of them im planning to get 4 charisma for dialogues (and security, gang etiquetes)
Should i also get 3 points in shamanism to het a totem? whith totem would be good for melle guy?

I can't really answer your melee Troll questions, but I've played as a decker a number of times in DF (on the hardest level, but should be applicable to normal). Note BTW that you can freely change difficulty levels after you've already started, so feel free to up the difficulty if it's too easy (you say you're a veteran of RPG+turn-based, so you'll find it too easy once you figure out the game mechanics).

Also BTW, the decker you find isn't lame at all - from memory even when I played as a decker, he would have stats at least equivalent to mine - but that could be because I invested a fair bit into charisma to pass the charisma checks. He also has a drone and SMG - he's not bad with the SMG, but his rigger skills are not that great. There is one mission in the game where having two deckers is useful, and you're correct in that having your PC with decker skills does indeed unlock extra content/money/etc. in some areas (but that could be said for a number of skills, including rigger, charisma, etc.).

1. I've started as both a human decker and an elf decker - both a viable. Elf trades off less starting karma for higher starting quickness. Technically the elf has a higher max quickness, but unless you focus on specialising you'll never reach the maximum with any skill no matter your character (I never did - it's definitely not required or even all that useful).

Assault rifles are definitely superior if you look at pure stats - they have higher accuracy and damage - their only downside is that the burst/auto modes requires 2AP (not a problem once you reach the point where everyone starts with 3AP, plus you have cyber/drugs/etc. to help on top of that - and before that point you probably won't need burst/auto really anyway).

I would definitely invest something in body, but as a decker (or as anyone with a focus on quickness and ranged weapons IMO) you won't need to invest all that much. Definitely don't make it a priority, unless of course you find yourself getting wiped out too easily. From memory I've completed most games (as decker or ranged street sam) with 3-4 at the start, 4 most of the game, then 5 later. I can't recall if I ever bothered getting it to 6. If you want to play it safe though, just ensure your body is about the same as the weakest member of your team (which I think is the punk shaman).

Personally I don't value dodge at all, since quickness not only increases your evasion but also increases your chance to hit with ranged weapons and increases your movement speed. Dodge increases evasion only (in HK it also reduces the chances of enemies targeting you - in that they will prefer to target whoeever has the lowest dodge - but I'm not sure if this is in DF already, and even if it is, I've gotten through it many times on the hardest level without worrying about it).

You can easily master (max or mostly-max) two of the three, if you also factor in that you want decent charisma to pass those charisma skill checks. If you want drones + decking + assault rifles, then maxing drones is a waste anyway since the higher levels give you access to two drones at once, which you won't be able to use unless you leave either your assault rifle or deck at home (you're limited to at first 2, then max 3 "weapons" at once - drones and decks count as "weapons").

Rigging does unlock some extra stuff, and the decker in your team (if you choose to bring him) won't be able to pass those skill checks. Not that you miss out on a lot as there are always other ways to go about this (no karma missed IIRC).

2. Can't answer this one entirely as rarely play melee or troll. I played a chi-casting dwarf once and he rocked though (that was the only character I used the "racial maximum" for - chi casting has special skills you can only get as a dwarf due to their higher magical aptitude - not that these were required though). Can't recall whether I went unarmed or weapons - both are definitely viable, with each one having many common and some unique "spells" for each type.

Come to think of it, a troll would probably be better with cyber than with chi casting (although either is definitely viable). Cyber isn't as good in DF as it is in HK (no awesome built-in cyber weapons unfortunately), but there's still some pretty good stuff there - some of it is even viable with a chi caster since it doesn't reduce your essence.

3. On charisma, I usually start around 4, and reach at least 6-7 or higher by the end - this is for the hardest level, so you might be able to get away with less on normal. That (along with the right etiquettes) should allow passing most/all charisma-related skill checks.

As for totem - depends on whether you need those karma points for something else. If you have points to spare then why not? I originally did that every time, but now I use them for other things unless I'm actually planning on using shaman skills. The totems themselves aren't anything special or game-changing, as most are rubbish - I think I generally went for one that increases chance-to-hit for all allies in range, that actually seemed useful.

The one thing that might caught you offguard is the skill requirements for various weapons.
For all firearms the skill is Ranged Weapons (although there might have been one or two with strength requirements).

So you can ignore weapon specific skills (like assault rifles) and still be able to use the best weapons.
The weapon skills open extra fire options, but you wont be able to take everything anyway.
(one really good combo for no-weapon-skills player is shotgun for close and sniper rifle for long ranges)

You really, really, really need:

Body, decent level is enough, this is your HP and without you will die easy.
Quickness and Ranged weapons, both to pretty high levels, enough to unlock the best weapons.

Intelligence and Decking, both to pretty high levels, to unlock the best decks and survive decking.

And then you need:
ESP control, so your program helpers when decking, are not useless.
Weapon specific skills, so you unlock stuff like full auto fire.
Charisma, to get through some dialogues.

And all the rest is fun to have too.

And splash out on Cyber. There's really useful stuff out there.
Although there too, much of the better stuff only comes available late game.

I found the NPC Decker that you save on the hotel/club mission to be quite OP when he is inside of the matrix. However, he is quite crappy when he is outside of the matrix.

All-out melee troll is pretty great. I don't remember the specifics of the one I made (except that he was using an axe), but I'm not sure it matters. They rip your enemies to sheds.

Out of the three games, I feel Dragonfall is the most suited for a Decker protagonist. Your character won't be very good at combat, but then again, you're probably not supposed to be.

I had a Sniper Decker and it is incredible how strong she was inside or outside of the matrix. And I tottaly agree how well suited is a Decker protagonist, since most of the unique/alternative shortcuit and secrets seems to be are avaliable to one. Wait to recruit the npc Decker is lose resources, but how much?

If you want to go nuts meta-game wise, it's perfectly viable to give someone decking skills as a secondary skill that's just high enough to pass those optional decker checks. I did that once with a combat mage of all characters (never brought or used a deck - just the skill).

Naturally to do this well requires some knowledge of what level these checks are at - so may need to look at the source for DF. From memory they're not as high as other checks.