Explanation
Adverbs are words which describe the action of a verb. They show how, when and wher things happen - e.g. "quickly", "often", "outside". You can usually recognise an adverb in English becuase it ends in "-ly" - e.g. "happily", "regularly", "completely".
This is not the case in German, wher most adjectives can be used as adverbs without adding a suffix. In fact, when such adjectives are used as adverbs they have no endings at all:
Anna ist eine gesunde Frau.
(Anna is a healthy woman (= adjective).)
Wir essen sehr gesund.
(We eat very healthily (= adverb).)
"Metropolis" ist ein guter Film.
("Metropolis" is a good film (= adjective).)
Es geht mir gut.
(I am very well (= adverb).)
Word order with adverbs
The positioning of adverbs in a German sentence can be tricky as German word order is quite specific on this point. For the moment it will suffice to note that if you put an adverb or adverbial phrase at the start of the sentence, then the verb must come next followed immediately by the subject of the clause. This is known as inverted word order.
Note too that German adverbial phrases are not separated from the rest of the clause by a comma when they occur at the start of the sentence.
Hoffentlich kommt das schöne Wetter noch.
(Hopefully the good weather will still come.)
Manchmal fahren wir in die Berge.
(Sometimes we go into the mountains.)
Im Moment ist es mild.
(At the moment the weather is mild.)
Zweimal in der Woche gehe ich zu einer Aerobicstunde.
(Twice a week I go to an aerobics class.)