Hello, Shao.
Sorry, I've talked too much about myself OR I've been talking about myself for way too long.
I haven't asked you how you've been so far (OR depending on where the 'so far' actually goes, you could also say: 'So far, I haven't asked you how you have been'.).
Your next sentence is correct but you could also say: 'It's been more than a week since we last talked'.
After a long pause, I'd like to concentrate on (talking about) my friend OR 'I'd wish to let my friend talk'. (To be honest, I was confused with what you meant here that's why I gave you two possible options).