anspruchsvoll
demanding
Setting high requirements and therefore difficult, complex, or time-consuming. It can refer to tasks, works, or situations.
Das Studium der Physik ist sehr anspruchsvoll.
Studying physics is very demanding.

demanding
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demanding
Setting high requirements and therefore difficult, complex, or time-consuming. It can refer to tasks, works, or situations.
Das Studium der Physik ist sehr anspruchsvoll.
Studying physics is very demanding.

The word is made up of 'Anspruch' (claim, demand, expectation) and '-voll' (-ful). So it literally means 'full of demands' or 'full of requirements,' which makes both meanings easier to understand.
Ein Marathonlauf ist eine sehr anspruchsvolle sportliche Leistung.
Running a marathon is a very demanding athletic achievement.
The meaning depends on what the adjective refers to. If it describes a thing or task, it means 'difficult' or 'complex.' If it describes a person, it means that this person has high expectations.
Dieses Computerspiel ist sehr anspruchsvoll und nichts für Anfänger.
This computer game is very demanding and not for beginners.
When something is difficult, 'anspruchsvoll' (demanding) is often combined with nouns such as 'Aufgabe' (task), 'Job' (job), 'Text' (text), 'Studium' (degree program/studies), or 'Training' (training).
Er hat einen sehr anspruchsvollen Job in der IT-Branche.
He has a very demanding job in the IT industry.
To describe a person with high expectations, 'anspruchsvoll' (demanding) is often used in combinations such as 'anspruchsvoller Kunde' (demanding customer), 'anspruchsvoller Chef' (demanding boss), or 'anspruchsvoller Geschmack' (refined/demanding taste).
Unser neuer Chef ist sehr anspruchsvoll, aber fair.
Our new boss is very demanding but fair.
simple / just
'einfach' and 'anspruchsvoll' both describe how hard or easy something is to manage. You use 'einfach' when a task, text, or process is easy to understand or do. You use 'anspruchsvoll' when something sets high requirements and needs more skill, time, or concentration. With tasks, courses, or projects, the contrast is especially clear: you can handle an easy task without much effort, while a demanding task challenges you more.

Der neue Kurs ist anspruchsvoll, aber sehr interessant.
The new course is demanding, but very interesting.
Die erste Aufgabe im Test war einfach.
The first task in the test was easy.