To get Domain Authority (DA) using an API:

Choose a Service: Use platforms like Moz, Ahrefs, or SEMrush, which provide domain metrics.
Sign Up: Create an account and subscribe to a plan that includes API access.
Get API Key: Obtain an API key or token for authentication.
Make Requests: Use the API to query DA for specific domains via tools like Postman or scripts.

If your positions dropped after implementing changes, it could be due to:

Algorithm Fluctuations: Search engines may take time to re-index your site.
Change Impact: Adjustments might have affected content relevance, structure, or user experience.
Redirect Issues: Improper handling of URL changes can disrupt backlinks.
Increased Competition: Competitors might have optimized.
Algorithm Updates: Rankings can shift due to external updates.
Incomplete Implementation: Changes might not align with SEO best practices