vernünftig
reasonable
Guided by reason and good judgment; sensible and well considered.
Es wäre vernünftig, vor der langen Fahrt eine Pause zu machen.
It would be reasonable to take a break before the long drive.

reasonable / decent
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reasonable
Guided by reason and good judgment; sensible and well considered.
Es wäre vernünftig, vor der langen Fahrt eine Pause zu machen.
It would be reasonable to take a break before the long drive.

'Vernünftig' is derived directly from the noun 'die Vernunft' (reason, sense). Something that is 'vernünftig' is therefore guided by reason.
Er hat eine Entscheidung getroffen, die von Vernunft geprägt ist.
He made a decision shaped by reason.
'Vernünftig' is often used as advice or an appeal, especially in the form 'Sei vernünftig!' (Be reasonable!). It also often describes decisions, plans, or people.
Sei vernünftig und geh nicht allein im Dunkeln nach Hause!
Be reasonable and don't go home alone in the dark!
In colloquial language, 'vernünftig' often means 'ordentlich' (proper/decent), 'richtig' (real/proper), or 'ausreichend' (sufficient). It then describes a satisfactory quality or quantity.
Ich brauche mal wieder eine vernünftige Mütze für den Winter.
I need a decent hat for winter again.
healthy
'gesund' and 'vernünftig' can overlap in a figurative sense. Both can mean that something is sensible, normal, or well considered. 'vernünftig' is used directly for decisions, behavior, or plans when someone acts with a clear head. In this sense, 'gesund' sounds more figurative, for example in 'ein gesundes Maß' (a healthy measure), 'gesunder Menschenverstand' (sound common sense), or 'eine gesunde Einstellung' (a healthy attitude). If you simply want to say that a decision is sensible, 'vernünftig' usually sounds more natural. 'gesund' fits better when something seems balanced, normal, or not excessive.

Nach der Arbeit hat meine Nachbarin eine vernünftige Lösung für das Parkplatzproblem gefunden.
After work, my neighbor found a reasonable solution to the parking problem.
Ein gesundes Maß an Pausen hilft beim Lernen.
A healthy amount of breaks helps with studying.