A portal is what you need. What you describe with your reservation is very similar to a Sales Invoice where you list multiple items sold for a single sales transaction. For that reason, you might want to examine the starter solution for Invoices that came with your copy of FileMaker for ideas that you can incorporate into your project.
But I don't know how can I add and delete a register in portals.
What is a "register"?
it´s a record, sorry. And yes I know that the starter solutions are to help us, but if you don't know the name of the tool that they are using you can't investigate how that tool works.
But which "record" do you want to delete? You have a record for your reservation and a record for each row in the portal. I would guess that you don't know how to delete records out of the portal.
For deleting rows from the portal, you can enable portal row deletion in Portal Setup. Then, if you click a blank area of the portal, you can select "delete record" from the records menu and FileMaker will delete the portal record after first confirming that this is what you want to do. But you can also put a button in the portal row that deletes the portal record. Delete Portal Row is an option that you can select in Button Setup.
You are welcome to download the known bugs list database and check out the portals found in the Bug Report layout. You'll see buttons that look like red X's that perform a script to delete portal rows. It's a bit fancier than the standard "delete portal row" button option but the script can be imported error free into other database files and used if you are interested in using it.
but if you don't know the name of the tool that they are using you can't investigate how that tool works.
And that's one of the reasons that this forum exists. So that people in your situation can ask questions and get some assistance. Feel free to ask more questions if you need further guidance.
Thanks, I'll download it and keep working. Thank you