"Learnings" is the plural of "learning" in the sense of "(specific) things or lessons that have been learned". It is often considered nonstandard English, even though it is rather widely used.

Is it correct to say learnings?

Yes, the plural of learning is learnings. It appears in established expressions like new learnings (a medical term).

Why are people saying learnings instead of lessons?

As the website The Grammarist, says: “Learnings is a pluralisation of an erroneous form of learning as a singular noun. Said singular noun (eg, a learning) does not exist, at least according to most dictionaries.