What is the usage scenario of "Shite imasu" ?

Usually I see "shite imasu" being used for the action which is continuous. However, I have also seen that only "imasu" being used. For example, to say "I am reading" we may say - わたしはよんでいます. But when I say that - "I have been studying", It is said as "benkyo shite imasu". Please explain with some examples if possible.

In both examples, "imasu" is used the same way: to give the sentence the meaning of continuity. "Shite", which is the "te" form of "suru", is only used as an auxiliary verb in "bekyou shite imasu". The word "benkyou" is not actually a verb, but a noun, so in order to make it a verb, you need to add the auxiliary verb "suru" to it. "Yomu" is a standalone verb, so there's no need for another auxiliary verb, that's why "imasu" is directly attached to "yonde". Hope this helps :)