handeln
to act
To become active, do something, or carry out an action, often in response to a situation.
Angesichts der neuen Informationen müssen wir sofort handeln.
In view of the new information, we must act immediately.

to act / trade
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to act
To become active, do something, or carry out an action, often in response to a situation.
Angesichts der neuen Informationen müssen wir sofort handeln.
In view of the new information, we must act immediately.

The verb 'handeln' (to act / trade) is related to the noun 'die Hand' (hand). The basic idea is doing something with your hands, that is, becoming active or carrying something out.
Statt nur zu reden, sollten wir endlich handeln.
Instead of just talking, we should finally act.
'Handeln' does not directly mean 'to handle' in the sense of 'dealing with something.' 'Handeln' means 'to act' or 'to trade.' If you want to say 'I can handle it,' in German you often say 'Ich schaffe das' (I can manage it) or 'Ich kann damit umgehen' (I can deal with it).
Die Politiker müssen jetzt schnell handeln.
The politicians must act quickly now.
The meaning of 'handeln' depends strongly on the sentence structure. On its own, it means 'agieren' (to act). With 'von + dative', it describes a topic. With 'mit + dative', it means trading in goods. The reflexive form 'sich handeln um + accusative' identifies something.
Der Film handelt von einer wahren Geschichte.
The film is about a true story.
The expression 'es handelt sich um' is a fixed, impersonal construction with the accusative. The 'es' at the beginning is obligatory and cannot be replaced. This form is typical of formal, factual language.
Bei dem Anrufer handelte es sich um einen alten Freund.
The caller turned out to be an old friend.
The construction 'handeln von + dative' is almost always used to describe the content or topic of a book, film, conversation, or story.
Wovon handelt dein Lieblingsbuch?
What is your favorite book about?
When 'handeln' means 'Geschäfte machen' (to do business), it is always used with the preposition 'mit' and the dative. The object after 'mit' is the goods that are bought and sold.
Mein Onkel handelt mit gebrauchten Autos.
My uncle trades in used cars.
to do / make
'machen' and 'handeln' can both mean that someone does something. However, 'machen' is very general and fits many normal activities. 'handeln' more often means that someone takes deliberate action, often because a situation requires a decision or response. It sounds more serious and somewhat more formal than 'machen'. The words can be confused because both describe an action. In everyday life, people often say 'etwas machen' (to do something); 'handeln' fits better with problems, danger, or important decisions.

Nach dem Unfall haben die Eltern sofort gehandelt.
After the accident, the parents acted immediately.
Nach der Nachricht macht sie zuerst einen Tee und ruft dann ihre Mutter an.
After the message, she first makes some tea and then calls her mother.