aufnehmen
to record
To record sounds or images with a technical device so they can be played back later.
Ich möchte das Interview mit meinem Handy aufnehmen.
I want to record the interview with my phone.

to record / take in
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to record
To record sounds or images with a technical device so they can be played back later.
Ich möchte das Interview mit meinem Handy aufnehmen.
I want to record the interview with my phone.

'Aufnehmen' is a separable verb. The prefix 'auf-' goes at the end in a main clause. In subordinate clauses and in the infinitive with 'zu', the verb stays together.
Die Kamera nimmt alles auf.
The camera records everything.
The verb consists of 'auf' and 'nehmen' (to take). The basic idea is often to 'take something to oneself' or 'take something in', whether it is a sound, a person, information, or a task.
Die Familie hat einen Flüchtling bei sich aufgenommen.
The family took in a refugee.
In the meaning of 'aufzeichnen' (to record), the objects are typically media content. For example, you can record a song, a video, a podcast, a photo, or a conversation.
Die Band nimmt gerade ihr neues Album im Studio auf.
The band is currently recording their new album in the studio.
When someone is admitted into a group or institution, German uses the preposition 'in' with the accusative.
Die Universität hat dieses Jahr viele neue Studenten aufgenommen.
The university admitted many new students this year.
The expression 'Kontakt aufnehmen' (to make contact) is always used with the preposition 'mit' and the dative to name the person or office being contacted.
Ich muss dringend Kontakt mit meinem Anwalt aufnehmen.
I urgently need to make contact with my lawyer.
In the sense of 'protokollieren' (to record officially), 'aufnehmen' is often used by official people such as the police. Typical objects are 'einen Unfall' (an accident), 'eine Anzeige' (a report/complaint), 'die Personalien' (personal details), or 'eine Aussage' (a statement).
Die Polizistin nahm die Aussage des Zeugen auf.
The policewoman recorded the witness's statement.
In this meaning, 'aufnehmen' is often used for starting or resuming a formal activity. Typical objects are 'die Arbeit' (work), 'den Betrieb' (operations), 'das Studium' (studies), or 'die Verhandlungen' (negotiations).
Die Fabrik hat nach der Sommerpause die Produktion wieder aufgenommen.
The factory resumed production after the summer break.
The idiom 'es mit jemandem/etwas aufnehmen' (to take someone/something on) is fixed. The pronoun 'es' must always be included. It means to face an opponent or a challenge.
Der junge Boxer will es mit dem Weltmeister aufnehmen.
The young boxer wants to take on the world champion.
to begin
'beginnen' and 'aufnehmen' can both express that something is starting. 'beginnen' is general and fits many actions, courses, conversations, or processes. 'aufnehmen' is used more in fixed expressions, for example 'die Arbeit aufnehmen' (to take up work / start work) or 'Kontakt aufnehmen' (to make contact). It can also mean continuing again after a break. Learners may confuse the words because both refer to a beginning. As a simple guide: for a normal beginning, 'beginnen' is usually safer. 'aufnehmen' sounds more precise when an activity officially starts, is continued, or a connection is established.

Nach der Pause nimmt das Team die Arbeit wieder auf.
After the break, the team resumes its work.
Der Deutschkurs beginnt am Montag um neun Uhr.
The German course begins on Monday at nine o'clock.