He talks as if he knows everything.

Source: Tatoeba

There are so many things to tell you that I don't know where to start.

I have so many things to tell you that I don't know where to start.

Source: Tatoeba

Speaking of Mary, I have not seen her for a long time.

Source: Tatoeba

That boy talks as if he were a grown up.

Source: Tatoeba