How do i delete threads/posts?

I cannot find the option anywhere when i click on "Edit".

I think you have to ask a moderator to do this.
In one of my threads I just asked in a post if a moderator could mark my thread [solved] - and he did.
... just realised where you posted ... sorry.

You can click the small red triangle next to the post to bring to attention to staff about any concerns.
However, do not abuse this.