SPOILERS || Quest support

[Virida]

I trei it for week  and it don´t work

Try what exactly?

This : QE QD XFB OFEJ CWO YBQGQULNL EX ABLCEPL UQML QWEX C WLH CNL XM LWUQNPELWVLWE.
The other Problem is i have Completed al quest an no extra spot

The quest that gives an extra slot is the one after the decryption one so it is correct that you do not have it yet. You can only see the quests you have unlocked so far, so even if it looks like you have finished all quests that is not necessarily the case.
There is an explanation of how to do the decryption in the FAQ linked in the first post, complete with a translated alphabet. Or have you already decrypted it and it doesn´t take it? If so please post what you have and I can look it over! :)