Help needed with the present simple tense and conjugations

[tal69]

Hi, guys. The book I am reading from gave me an example of a sentence from the present simple tense, here it is: ' leo una revista. ' it was translated as saying ' I am reading a magazine.' shouldn't this sentence be used within the present progressive? The book I'm learning from describes the present progressive as, ' is used to describe what is happening an the moment, an action in progress '

The sentence ' I am reading a magazine, leo una revista ' is describing what is happening in the moment and it is stating an action in progress.

and my second question, why does the verb 'estar' employ the conjugations from the present simple? example, ' ella esta hablando ' the verb esta states that it a he/she is the subject, but I thought that the conjugations changed depending on what tense you use?

I hope you understand, thanks so much in advance. This is my 4th day learning Spanish, and I'm just eager to clear this up