I will read some of these tips. Thank you

That's a good tip. I usually stop what I'm reading to look for the meaning of the word. I think this attitude makes it harder for me to really understand the meaning.

Does anyone know any Bahia food restaurant in the Bay area?

In my opinion the essay is a very difficult stage, in my case I always speak informally and to write I always feel that everything is very informal. I know I should practice more to make this natural for me.

Sausalito! Rent a bike and go to Golden Gate

This is a good point.
I learned only "hello" and "hi" and also "how are you?"
And when you meet Americans they came you "what's up" "what's going on?"
its fun, as much you met more people more ways to greet you can learn.

What is the hardest word to pronounce for you?
for me: Squirrel

How many words do I need to learn to have vocabulary as rich as native speakers have? I'm probably at upper intermediate level.

As a student, I can say that grammar and some accents are the hardest to improve.
I'm sure I've already learned all the grammar, but there are some situations where I prefer to talk quickly, and in those situations I forget the correct grammar.