##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 

 1. keep prepared the ones you had the day before, or
 2. 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, 2d, and 3d level spells that equals 9.  For example, pick 7 1sts and a second and a third, 6 seconds and two firsts and a third, and so on.  You can still only cast the spell slots you have; 4 firsts, 32 seconds, and 2 thirds.      

> 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.