Your level 5 druid knows all spells on the Druid Spell list ...
... from levels 1, 2 and 3.
The problem you have is: which ones does the druid prepare on a given day?
How to translate the rules?
You have to make choices after each long rest to either
keep prepared the ones you had the day before, or
prepare a different set.
This makes playing a druid (and a cleric) require a little more thought, and some forecasting, to try and have the right spells prepared for a given adventure.
Preparing and Casting Spells
You prepare the list of druid spells that are available for you to cast, choosing from the druid spell list.When you do so, choose a number of druid spells equal to your Wisdom modifier + your druid level (minimum of one spell). The spells must be of a level for which you have spell slots.
Let's assume a Wisdom score of 18 for a 5th level druid. You can prepare nine spells. You have to choose a combination of 1st, 2nd, and 3rd-level spells that equals 9. For example, pick 7 firsts and a second and a third, or 6 seconds and two firsts and a third, and so on. You can still only cast them with the spell slots you have: 4 first-level slots, 3 second-levels, and 2 third-levels.
You can also change your list of prepared spells when you finish a long rest. Preparing a new list of druid spells requires time spent in prayer and meditation: at least 1 minute per spell level for each spell on your list.
Choose what you think will help your party the best.
