Use the Present Progressive it to talk about things that are happening right now! Think of it as progress in the present: working, shopping, talking, studying.
The Present Progressive is roughly equivalent to the ing ending in English. It's easy to learn. There are no irregular verbs in this tense! Even more good news:
Using the Present Progressive
*SUBIR often takes the meaning of coming up as in: coming up the elevador.
The verb estar is always right before the verb in the this tense. That's because the grammar is identical to English in that you/he/she/we/they are doing something. The formation is totally consistent and there are no irregulars at all.
Forming the Present Progressive
|She's arriving||Ela está cheg||ando|
|Who's talking?||Quem está fal||ando?|
|I'm eating.||Eu estou com||endo|
|He's losing.||Ele está perd||endo|
|He's insisting.||Ele está insist||indo|
|She's driving.||Ela está dirig||indo|
You can also use the Present Progressive when talking about the past!
You can place it in the past when describing what was happening. In this case ESTAR is going to be in the imperfect past tense because you'll always be talking about action that was ongoing in the past:
*It's understood that the action was ongoing because in a sentence like this you are really saying something like, I was trying to call you (yesterday, when I was driving to work). If you just wanted to say that you tried to call yesterday you would say, Eu tentei te ligar.
*Again, this is in the context of a conversation in which it's being said that "She was sleeping when something else..."