oft
often
At many different times; frequently or several times.
Wir gehen oft zusammen ins Kino.
We often go to the movies together.

often
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often
At many different times; frequently or several times.
Wir gehen oft zusammen ins Kino.
We often go to the movies together.

As an adverb, 'oft' (often) can stand in different positions in the sentence. If it is in position 1, the verb follows directly. If it appears within the sentence, it usually comes after the verb and the subject.
Oft denke ich an unsere Reise zurück.
Often I think back to our trip.
The comparative form of 'oft' (often) is 'öfter' (more often). This form is used very frequently to express that something happens 'even more frequently' or 'several times'.
Früher war ich nur selten hier, aber jetzt komme ich öfter.
I used to be here only rarely, but now I come more often.
You can strengthen or weaken 'oft' (often) with other words. Typical combinations are 'sehr oft' (very often), 'ganz oft' (very often), or 'nicht so oft' (not so often).
Wir gehen nicht so oft aus, weil wir kleine Kinder haben.
We don't go out that often because we have small children.
much / a lot
'viel' and 'oft' can both have to do with repeated actions. 'oft' clearly says that something happens frequently, meaning at many points in time. 'viel' describes more the amount or intensity of an action. In some sentences, both are possible, but the focus is different: 'Ich lese oft' means that I read frequently. 'Ich lese viel' means that I read a large amount overall or read for a long time. Learners confuse the words because both can appear before or with verbs. If you mean frequency, use 'oft'. If you mean amount or duration, use 'viel'.

Du kommst oft zu spät, weil der Bus morgens voll ist.
You are often late because the bus is full in the mornings.
Seit dem neuen Kurs lernt Mehmet viel für die Prüfung.
Since starting the new course, Mehmet has been studying a lot for the exam.