Question about how things work here

Perhaps I'm overlooking something obvious so forgive me for these questions -

1) If I make a mistake in posting how do I edit it? What worries me is some mistakes can completely change meaning, leaving out a word for example. Given the nature of this site this can hurt feelings and mislead people and damage reputations, all kinds of problems. How can this be avoided. I'm older now, and I make more mistakes than I used to, sometimes not even using the right word even though my brain knows it but my fingers are woefully out of shape.

2) Is it possible to delete a thread after its relevance is lost? This might be important to me because I am new here and there are a lot of things on my mind and I want to participate and share in my struggles and learn from others too. I'm really hoping to encourage others to share their thoughts at times. But if editing isn't supported, is deletion possible?

If anybody knows I would appreciate some help, or start a conversation where lessons learned can be exchanged.

Thank you - LostThomas