I see that every time I phrase these sentences so that they have an infinitive in English, DuoLingo suggests another correct sentence which does not.
Is the "another correct solution" the "preferred solution" or would it show another correct solution no matter which sentence I put?
vanligvis = usually pleier å gjøre = tend(s) to do An adverb is used in ways surely different from those in terms of a verb. As for the nuances in meaning, unenlightened here, too!
Just a 'friendly' reminder you might find useful: A little typo can 'usually' turn a word into a barely related other ;) (vanlig~vennlig)