Are there many idioms in English?
There are hundreds and hundreds. English is particularly rich in idiomatic expressions.
Can you give us an example?
I'll look up the rate. To look up doesn't mean to look high into the sky or to look at the roof. It means to search for and find some information.
What about the expression ' goodbye '? Is that an idiom?
That is just a natural, grammatical English expression. It has a direct translation in other languages.