angehen
to concern
To affect someone or be of importance to someone. Often used in questions or negations.
Deine privaten Probleme gehen mich nichts an.
Your private problems don't concern me.

to concern / turn on / tackle
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to concern
To affect someone or be of importance to someone. Often used in questions or negations.
Deine privaten Probleme gehen mich nichts an.
Your private problems don't concern me.

'Angehen' is a separable verb with the prefix 'an-'. In main clauses, the prefix stands at the end of the sentence. In subordinate clauses and infinitive constructions, the verb stays together.
Die Heizung geht bei Kälte automatisch an.
The heating turns on automatically when it is cold.
In the meaning 'betreffen' (to concern), 'angehen' (to concern) is always used with a person in the accusative. The most common form is the negation: 'Das geht dich/mich/uns nichts an.' (That doesn't concern you/me/us.)
Was ich in meiner Freizeit tue, geht niemanden etwas an.
What I do in my free time doesn't concern anyone.
When 'angehen' (to turn on) means that something begins to function, the subject of the sentence is usually a technical device, a light, or a fire. In this meaning, the verb is often used without an object.
Mein alter Laptop geht nur noch sehr langsam an.
My old laptop only turns on very slowly now.
In the meaning 'begin to deal with something,' 'angehen' (to tackle) is often combined with abstract nouns such as 'Problem' (problem), 'Aufgabe' (task), 'Projekt' (project), or 'Thema' (topic). The noun is in the accusative.
Die Firma muss das Thema Nachhaltigkeit strategisch angehen.
The company has to tackle the topic of sustainability strategically.
The expression 'was ... angeht' (as for/regarding ...) introduces a topic. The verb 'angeht' stands at the end of this subordinate clause. The following main clause can then begin normally.
Was die Planung für das Wochenende angeht, bin ich für alles offen.
As for the planning for the weekend, I am open to anything.
When 'angehen' (to take action against) is used in the sense of 'kämpfen' (to fight) or 'protestieren' (to protest), it always appears with the preposition 'gegen' (against) followed by an accusative object.
Die Organisation geht seit Jahren gegen die Umweltverschmutzung an.
The organization has been taking action against environmental pollution for years.
to begin
'beginnen' and 'angehen' can both mean that you start something. 'beginnen' is more general: a course, a conversation, a piece of work, or an action can begin. 'angehen' is used especially when you actively tackle a task, a problem, or a project. It suggests: now you are dealing with it. Learners may confuse the words because both describe a beginning. If only the start is important, 'beginnen' fits. If it is about dealing with a problem or task, 'angehen' is more precise.

Nach der Besprechung geht das Team das neue Problem gemeinsam an.
After the meeting, the team tackles the new problem together.
Der Kurs beginnt morgen um neun Uhr.
The course begins tomorrow at nine o'clock.