Development Mode

Hello,

In Caching/Configuration I read
" Development Mode

Temporarily bypass our cache allowing you to see changes to your origin server in realtime.

Note: Enabling this feature can significantly increase origin server load. Development mode does not purge the cache so files will need to be purged after development mode expires."

I am however experiencing the other way about. When I set Development Mode to OFF my site takes half the time to load. When I set it back to On it can take 10s (when it is on, it can take 6.75s)

I have no experience at all . Perhaps I should configure the tabs I see:
Rules, Firewalls, Access, Workers, Speed, Custom Pages, I would appreciate your help please.

Thank you very much

Liliana