maybe a tech support could open a ticket for my email adress if he sees this?
A Community Manager says posting one's e-mail address is OK but not according to a lower ranked admin who's inventing rules again. You ask for help and not only isn't he helping you get your issue resolved quicker but he's actually standing in your way. Even if a tech support rep bothers to read the forum out of boredom, Vayus has made sure you wouldn't receive any help. Congrats! 
Hello people, I don't know how to deal with my problem, so I thougt asking community would be may be helpful.
Hey there,
Where are you from - Baguetteland perhaps? Why are you playing on Seren? If you do speak French, you can explain your problem in the French section of the forum.
Assistance technique entre joueurs
Who knows, maybe you won't get the kind of "help" you got from the EN admin. Judging by how stupidly they closed the PS4 thread but ignored the one with a launcher issue, it's safe to assume you'll also get ignored. If you say 'can be closed' though, they'll rush in to "help," I promise you. 
Now that we've set the right expectations, can we move onto looking for a solution to your problem.
2 days ago a new player (from Hungary) approached me on Discord about the 'Termination code 5 (DirectX)' error. We sorted the issue and he could join the game. Literally 2 hours later another dude, a semi-returning player (this time from Poland) contacted me about the very same error. What are the odds, eh? 
Anyhow, it turned out this wasn't his only problem. After dealing with that error, the game wouldn't still start. There was no error anymore, no nothing. As soon as he tried to log in, the game client wouldn't even make an attempt to start (we were monitoring his task manager to see if the process starts at all). We tried logging into his account on the main website - we couldn't (delay creating account or something message). Oh, btw, they both got the game via Steam. Then I asked him to try logging into the 'old' account management - it let him in but it said there was no game account associated with his profile. Like wtf. We assumed his account might have even been deleted. Since he had some low level char before, he didn't really care about that account, so he just created a new one as an alternative to going through Support trying to recover his old account. Since the 'code 5' error was no longer present, he could log into his new account effortlessly and thus re-join the game. 
OK, I'm not too sure any of the above is relevant to you (haha) but you should be prepared that your old account has been lost. This said, try creating a new one with a different email address (don't create multiple accounts at once though!!) and see if you can log into the game. You can then contact Support (in French) about your old account. Yes, I know you "can't" contact them. First, game/website account is different to your Support account. Second, you can always create another Support account and use it to contact Support about your other account, provided you can prove you're the owner of it. I've done it before, so it's fine. 
Not going to go into too much detail about the 'unexpected' error, as it could mean a lot of things, including connection problems, hosts file, banned account, naughty anti-virus/defender/firewall, which might not even be related.
TERA launcher issues made simple - error messages explained, plus Steam players notes
Good luck! 