Hi guys,

ive finished Grim Dawn the first time with my demolitioner after a long period. The reason was big probems in endgame with my char. The most mobs killed me easily, If I not spam the healing and energypotions.

Can you take a look on my chars stats and skills and tell me whats wrong with it?

Everything.
1. No second mastery + your only one isn't maxed. You are missing tons of free health from mastery bars.
2. Definitely no augments, you should farm faction reputation. They give ton of resists.
3. Yellow items. Since you completed game quest, you can buy faction gear. It would be tenfold times better than what you have
4. No components in most items, and the ones you have are garbage. They give tons of resists and dps, you are missing a lot of survivability.
5. Devotion is utterly useless. Anvil is for people with shield, Crook is for summoners. The rest is fine, but doesn't unlock anything good for you. If you are going for two-handed rifles, your first priority is getting Kraken. It is more than 200% dps boost. https://i.imgur.com/JJFWsqn.png
6. You are using two-handed ranged weapon and have 3 points in searing strike, which needs one-handed melee weapon to be active
7. The rest of skills... Fire strike demolition mastery would look like that http://grimcalc.com/build/1009-mplIY3
Explanation:
Vindictive flame for small total speed bonus and occasional knockdown
Maxed flashbang for -defensive ability, more crits
1 point in canister bomb for stun
Blackwater cocktail =0, you aren't geared for it.
Static strike... Not worth it. Bosses/heroes have heavy resist to knockdown, its dps boost is abysmal (chance for some lightning and +50% fire, since you already have +100 from flame touched and +120 from kraken , it's change from 320% to 370% fire, +15% fire dps)
Brimstone - doesn't have %weapon damage component, so will fail short eventually, also not worth getting.

I agree with everything, exept:

Brimstone is absolutely worth getting, especially high levelled, because of the multiple projectiles it spread on the battlefield. They will proc the Devotion skill you have on Fire Strike, for example Fissure, which will stun everyone. But I admit it is even better while dual-wielding guns.
I use this and the Canister Bomb maxed (for added fragments) and Concussive Bomb maxed for even more stun, everywhere.

First of all, a big thank you for your time and the explanations.
Apparently I was not as "deep" into the game and the mechanics as I should. I take a look at every point of your answer and changed, what I can change in a short period of time.

1. Mastery bar is maxed now. Second mastery wasnt my wish. Is it really necsassary to have one? What is your recommendation for me? I want to play a two-handed ranged class as before.
2. In my first run of GD, I just played the quests. In most cases I could only take items from the second window.
3. Thats for sure. But I didnt found better items... Couldnt find a better two-handed ranged weapon for the last 3 hours I think.
4.I filled those gaps now.
5. Fixed.
6. embarrassing... changed that.
7.fixed that. Now I have lots of unused points. Think I spare them for my second mastery?

Again some screenshots of my Char. Note: I just played 1 hour or so but I can say: the flow is much better now!

1. Absolutely needed. Occultist, Shaman, Soldier or Inquisitor if you have expansion.
2. Farm reputation. You have notice boards and favorite enemies.
3. Factions sell weapons, but not sure if any of them is gun/crossbow.
7. Put one in Static strike, rest into Brimstone and Blast Shield.

Instead of screenshots try http://www.grimtools.com
It lets you link your character's equipment, skills and devotions in one go.

1. It is absolutely needed, mostly for stats if you don't want skills. I assume you don't have expansion since you are doing screenshots in elite instead of doing expansion.
Your choices:
Soldier - biggest chunk of additional hp, some resists, good auras, chance for additional on-hit damage (Markovian's advantage and Zolhan's techinque)
Shaman - good defensive stats and really good passives for two-handed, albeit they are going into lightning damage (you would need to get static strike back then)
Arcanist - amazing mastery for critbuilds. 1 point in Iskandra's exchange, max Elemental balance; max inner focus (offensive ability increases your chances to hit, to crit and to do bigger crit); Mirror of ereoctes - one point wonder, 3 seconds of invulnerabilty; maiven's sphere is good defensive aura.
Occultist - I wouldn't recommend for your current character.
Nighblade - I wouldn't recommend for your current character.

From these I strongly recommend arcanist, you would be able to wear out any enemy in the game by going mirror - 3 seconds of punishment - death - resurrect, mirror again.
Demo+Shaman would need Ultos legendary items, not sure that you would play that long to get full set.
Demo+soldier is the least playstyle change for you. just activate 2 skills upon login, and that's all.

2. Buy writs as soon as they available and do bounties (don't pick them without reading! some take really rare items away from you). After you max reputation, mandates would let your next characters get reputation at double speed, something around third tier reward by the end of main quest.
3. Go to Normal+veteran and run around necropolis, kill trolls with fire rifles. They drop "Fleshwarped incinerator", which adds +4 levels to flame touched and whopping 400+ hp. If you get this gun with good suffixes, it can serve you well until level 70+, where next tier incinerator drops. Another variant - go to blacksmith and ask him to craft two0handed rifle. Good chances that you would get an upgrade.
7 go for it.

A gift XD https://i.imgur.com/bILeR1U.png

Small howto about item management:
Game stores items in shared stash in transfer.gst
You can freely replace that file while being in game, just without stash opened.
I have couple of dozens folders with different items, like "epic pants", "epic caster offhands", etc.

So. Find transfer.gst for your character, create folder "trash", and backup it there.
rename attached transfer.jpg to transfer.gst and place it where transfer.gst for your character stored.
Pick your rifle XD

If he is a casual player and doesn't plan to play game to get all the gear, then the Soldier is better choice than the Arcanist, especially considering his choice in constellations.

Im very surprised about your help here. Thanks again.

@Gremlion: I didnt take the gun, cause I want to loot by myself :D

@both: Second mastery is soldier, cause I wanted the additional health and defense. Actually im at level 50 and it brings much more fun!

I think im a casual player at Grim Dawn, thats true. Played 26h. My last "Non-casual" ARPG was Diablo 2 and Expansion with over 500h. Im searching for a replacement. ;)