How long did it take you to learn English in order to speak it fluently?

Why do I feel relaxed and refreshed when reading complex books that require deep comprehension, while easier books leave my mind feeling overwhelmed, as if flooded with trivial content?
I’ve noticed that my GF often looks at other men when we’re out. I brought it up before, but she still does it just more discreetly now. Is this a red flag, or am I overthinking it?
What is one small, unexpected habit or quirk you've noticed in people recently that made you smile or think?