Hello @Gabryel, Andrzej and welcome back to Microsoft Q&A.
If I understand correctly, what you really want to know is, "How do I get the file name from an event trigger?"
For documentation, see step 10 and step 11 in how-to-create-event-trigger.
The idea, is to pass the filename and/or folderpath into pipeline parameters from the event trigger. Then you pass these pipeline parameters into your datasets through the activities.
So, step 1: create some pipeline parameters
Step 2: From your pipeline editing screen, do either new trigger or edit trigger. It is important you do it from the pipeline editing screen and not the manage > triggers screen because we want to use the context of your pipeline to set the parameters. In the last stage of creating/updating the trigger you can specify the value of parameters. We want to use:
Step 3: we need a parameterized dataset
Step 4: pass the pipeline variable into the activity to be used in the dataset parameters