Previously, I learnt basic expressions like “アダムさんは先生です。”,”アダムさんは医者ですが。” I thought は functions like “am/is/are” in English. But when I start learning Japanese verb this morning, I got a bit confused. “ひろしさんはテレビを見ません。” what is は’s function in this sentence?
は absolutely, definitely does not mean 'am/is/are'. That role is played by です in your example sentences.
は marks the topic of the sentence i.e,
Thing I want to talk about は what I want to say about it.
There is no equivalent concept in English so it causes a lot of confusion for many Japanese learners. It is commonly translated (very clumsily) as 'as for' e.g.
As for Adam, (he) is a teacher. = Adam is a teacher.
As for Adam, (he) is a doctor, but ... = Adam is a doctor, but ...
As for Hiroshi, (he) doesn't watch television. = Hiroshi doesn't watch television.
In all these examples I'm marking the thing I want to talk about (i.e the person) with は and then saying something about them.
The topic doesn't have to be just a single noun. It can be a long and complex phrase e.g. "As for that man stood on one leg on the edge of the mountain over there は he's going to fall off."
If you're learning from a resource that just teaches you phrases without teaching you the grammar properly, you're going to enter a world of pain.
Finally, here's a link that we normally send people to look at on は/が related questions. It may be a bit confusing at this stage, but it might help.
I wonder if アダムさんは医者ですが was a typo for アダムさんは医者ですか. The latter would obviously be "As for Adam, is (he) a doctor?" = "Is Adam a doctor?".