Grammar fix
get down to
start focusing on
to begin giving serious attention or effort to something, especially after a delay or distraction.
phrasal verbB1common

Hear it in context
Notice where the phrase sounds natural.
After chatting for a while, we finally got down to business.
In my opinion, when students get down to studying early, they usually achieve better results.
Fix the pattern
One small grammar move makes it sound right.
Not: It's time to get down to study.
Say: It's time to get down to studying. / get down to work.
'Get down to' takes a noun or '-ing', not a bare verb.
Which sounds natural?
Tap the one a native speaker would say.
'Get down to' is the natural phrase for buckling down; 'commence serious work on' is ceremonial.
Build natural chunks
Words that usually travel with it.
get down to + task
- business
- work
- the details
- it