I do not know when I have to use the present perfect simple (and others tenses in perfect form). I normally use: present simple, present continuous, past simple, past continuous, future, ... for write/speak. I hardly ever use tenses in perfect form.
So I imagined a real world situation for work with present perfect simple. I will work with these present perfect simple grammar rules:
We use the present perfect simple to talk about our experiences up to now. The time of the experiences is not important:
Recent completed events
We use the present perfect simple to talk about a finished event or state in the very recent past. We do not give a specific time. We often use words like just or recently for events taking place a very short time before now:
Past events, present results
We use the present perfect simple when a single past action has a connection with the present:
Source: Present perfect simple
(Situation: I work at GlobalTech company as software developer in the development department. In this conversation workmates and me discuss about a meeting between our development department's leader and the company's boss. NOTE: Developer department's leader is Javi and Company's boss is Manuel)
Me: (I am working in a project...) Oh my God, this problem again, I have fixed this problem many times... This is worse than a nightmare.
Javi: (He comes to our department after a meeting with Manuel...) Listen! I have talked with Manuel about the project which we are working with... We have decided that the deadline will be the next week, ok.
Javi: I will come in a moment, see you now.
(a few days later...)
Workmates: We can not more, we are working so hard, we will not achieve to finish the project for the next week. We do not understand why they have decided a project's deadline without our opinion. We have to talk with Javi.
Me: Yes, we MUST.
I will explain which present perfect simple's grammar rules I used for each one:
I have fixed : "Experiences". I got a problem in that moment and I said that I had the same problem many times before.
I have talked AND We have decided : "Recent completed events". He is talking about a finished event (a meeting) in the very recent past.
they have decided : "Past events, present results". Because both leaders' decision (some days ago) was causing burnout over us (in the present).
So I ask you: When I used the present perfect simple, Do you see them as a good choice in that conversation?