Then you show up and discover they only have one sedan available and it's got 200,000 kilometers on it, or their office is closed until noon because the guy who runs it had a doctor's appointment. Dealing with unreliable local operations when you're on a tight schedule just adds stress you don't need. You can rent a car in Amadora here:
https://getrentacar.com/en-US/portugal/amadora . You can connect with different car owners and rental companies in the area so you've got actual options to choose from. Book something that fits your schedule, pick it up when you need it, handle your meetings and drop it back when you're done.