der Rummel
fair
A public festival with rides, stalls, and other attractions; a funfair.
Die Kinder freuen sich schon seit Wochen auf den Rummel in der Stadt.
The children have been looking forward to the fair in town for weeks.

fair / fuss / junk
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fair
A public festival with rides, stalls, and other attractions; a funfair.
Die Kinder freuen sich schon seit Wochen auf den Rummel in der Stadt.
The children have been looking forward to the fair in town for weeks.

While 'Rummel' (fair) as a term for a public festival or funfair is standard German, the meanings 'Aufregung/Hektik' (excitement/hectic activity) and 'unnütze Dinge' (useless things) are colloquial.
Ich verstehe den ganzen Rummel um diesen Influencer nicht.
I don't understand all the fuss about this influencer.
When a fair is meant, German uses 'auf dem Rummel sein' (to be at the fair) for the location and 'zum Rummel gehen' (to go to the fair) for direction.
Wir waren gestern auf dem Rummel und sind Achterbahn gefahren.
We were at the fair yesterday and rode the roller coaster.
In the meaning 'Aufregung' (excitement/fuss), 'Rummel' is often used with the preposition 'um' + accusative. People make 'einen Rummel um eine Person' (a fuss about a person) or 'um eine Sache' (about a thing).
Die Medien machen einen riesigen Rummel um die königliche Hochzeit.
The media are making a huge fuss about the royal wedding.
In the meaning 'Kram' (stuff) or 'Plunder' (junk), 'Rummel' refers to a disorganized collection of things. It is often used in requests to tidy up and has a derogatory tone.
Bitte nimm deinen ganzen Rummel vom Tisch, wir wollen essen.
Please take all your junk off the table; we want to eat.
business / operation
'der Betrieb' and 'der Rummel' can both mean that there is a lot of activity and commotion. 'Betrieb' describes more neutrally that there is a lot going on in a place. 'Rummel' often sounds colloquial and can also mean that too much fuss is being made about a person or thing. If you only want to say that many people are there, 'Betrieb' works well. If it is about attention, hectic activity, or exaggerated interest, 'Rummel' is more precise.

Den ganzen Rummel um den neuen Film versteht Tom nicht.
Tom does not understand all the fuss about the new film.
Vor dem Kino war am Abend großer Betrieb.
In the evening, there was a lot of activity in front of the cinema.