dumm
stupid
Not very intelligent or clever; showing poor judgment.
Das war eine wirklich dumme Antwort auf eine einfache Frage.
That was a really stupid answer to a simple question.

stupid / unfortunate
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stupid
Not very intelligent or clever; showing poor judgment.
Das war eine wirklich dumme Antwort auf eine einfache Frage.
That was a really stupid answer to a simple question.

Using 'dumm' (stupid/unfortunate) for an unpleasant situation or in the expression 'sich zu dumm sein für etwas' (to be too good for something) is mainly colloquial. In more formal contexts, you would choose other expressions.
Dumm, dass ich meinen Schirm vergessen habe.
How annoying that I forgot my umbrella.
'Dumm' (stupid) can describe a person's trait or evaluate a single action. 'Er ist dumm' (He is stupid) is a strong, general statement about a person, while 'Das war dumm' (That was stupid) refers only to a specific action.
Es war dumm von mir, den Schlüssel zu vergessen.
It was stupid of me to forget the key.
When 'dumm' (stupid/unfortunate) does not refer to a person or an idea, but to a situation or event, it means 'annoying' or 'unfortunate'. A very common phrase is 'dumm gelaufen' (that went badly / bad luck).
Wir haben den Bus verpasst, das ist echt dumm gelaufen.
We missed the bus; that was really unfortunate.
The idiom 'sich für etwas zu dumm sein' does not mean that someone is intellectually incapable. It expresses that someone considers something beneath their dignity or simply doesn't feel like doing it.
Ich bin mir zu dumm dafür, drei Stunden für ein Handy anzustehen.
I'm too good for standing in line for three hours for a phone.
stupid / annoying
'dumm' and 'blöd' can both describe a person, an action, or a situation negatively. For people, 'dumm' more strongly means that someone acts unintelligently or understands little. This can quickly sound harsh and insulting. 'Blöd' is more colloquial and is very often used for annoying situations, for example when something goes wrong. But it can also describe a person or behavior as stupid, silly, or childish. Learners may confuse the words because both fit in sentences like 'Das war dumm/blöd' (That was stupid/annoying). As a practical guide: for an unwise action, 'dumm' fits well; for an annoying or unpleasant situation, 'blöd' often sounds more natural.

Es war dumm von mir, den Schlüssel im Auto zu lassen.
It was stupid of me to leave the key in the car.
Nach dem Essen war die Stimmung blöd, weil niemand mehr über den Streit sprechen wollte.
After the meal, the mood was awkward because no one wanted to talk about the argument anymore.