You cannot delete your account and your related threads.

You can edit your account information to keep/reveal as much as you like, and you can lock your account permanently, as described in False Passwords Void / Method to Disable Your Account.

Your threads and replies are kept and should not be deleted. See (tye)Re: why a nodelet can be kept against author wish? for discussion.

Also, Milan, it did seem to me that your (only, so far) thread was useful, and I think it got good answers, which of course makes it useful for similar questions as they inevitably will crop-up again in the future.   Which is really what this entire site is all about.   Even though perhaps English isn’t your primary language, that’s fairly common, too.   (This is a truly international community.)   Please continue to participate here as you see fit.   Welcome to the Monastery!

FWIW, its a multi account issue, see Re: not defined Hash data came why? and mak.jordan's writeups