The way people view time differs a lot by culture. After marrying a Portuguese and having many Portuguese, Spanish, and Italian friends, I actually had the opposite problem when I moved to Germany. If you set a meeting time, Germans will arrive 5-10 minutes early. At best, I would arrive at exactly the specified time but would usually arrive 5-10 min late. This led to a lot of confusion and frustration for everyone.
I can confirm that the Portuguese concept of time is very different from American and German concepts of time. If a German hosts a party at 17:00, then the guests will arrive at 17:00. If you are late, you will contact the host as soon as possible and offer many apologies for your tardiness. If a Portuguese hosts a party, it will probably start much later (not unusual to start at 20:00 or 21:00). If you actually arrive at 20:00, then you will find a surprised and probably unprepared host. It is the norm to arrive 30 min or even an hour late, depending on the type of event.
I know it is hard to adjust, but I assure you that this is not a personal insult to you. This is not a sign that people don’t respect your time and schedule. It also does not mean that the Portuguese are bad at business or are lazy or don’t take things seriously. It is simply a difference in cultural expectations. The Portuguese are incredibly hardworking, can be extremely savvy businesspeople, and are known for being very good diplomats. (There are many reasons why the Portuguese economy is sluggish, but cultural perceptions of time is not one of them.)
Chances are the frustration and feelings of being insulted run both ways. To you, the Portuguese don’t respect your time and schedule. To them, you are probably too pushy and “pesado”. The way to deal with it is to learn more about Portuguese culture, particularly their concept of time and business culture, and then adjust your expectations and actions accordingly. Do not expect the Portuguese to become American because, after all, you are living in Portugal.
This is a very common problem! So much so that there are a lot of resources about dealing with cultural differences in business to help people understand the different business approaches to avoid these kind of cultural misunderstandings. I think it would be useful to read about this. Knowing what to expect and how to interpret their behaviour is a good first step.
After that, you can try to slowly let go of the strict time schedule. Try to embrace and even master the new culture. This doesn’t mean you have to completely give up your business culture. You may find it useful to learn how and when to switch from American businessman to Portuguese businessman. If you work in an international business environment, this could be a very valuable skill!