How long will it take to see results? / What does a "90-day learning phase" mean?

Technically, you’ll start to see results right away; however, it takes about 90 days for a campaign to “normalize” to the point of understanding how it will perform long-term.

What are Dynamic Search Ads (DSA) Campaigns? When should I use DSA?

DSA Campaigns are used as learning experiments - You may choose to build dynamic search ad campaigns because they help you learn what ad copy & keywords to use in the other campaigns, in case you missed any important and effective words.