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Yes.

Hello Kekel and Feebs!

I don't understand why they are correct..

In the first sentence it says that the person is

Hi,

You really can't judge any of these sentences without some kind of context. For example, these contexts.

It's 10pm. Let me tell you what I do every evening. I go to sleep now.
I love Mary. Let me tell you what I do every Sunday. I go to visit her.

Hello Clive!

..but, without a context, would those sentences be correct?

Thanks in advance!

Yes. They are all understandable and make sense.

CliveIt's 10pm. Let me tell you what I do every evening. I go to sleep now.

Thanks for answering, Feebs!

It shows that at this moment you go to sleep.

But, can you use the word 'now' in an habit?

Hi,

Well, I was perhaps stretching things a little bit, to make my point about context.

But still, it wouldn't so

Hello Clive!

So, that means that 'now' can always substitute 'at this time', right?