The phrase "lot of learning" is correct and usable in written English. It can be used when referring to a great deal of knowledge gained from study or experience. For example: "I've done a lot of learning since I started my new job."
It took a lot of learning.
Again, I did a lot of learning.
I have a lot of learning to do.
"There's a lot of learning material there," Porter said.
"There's a lot of learning that's going on right now.
"It's going to inevitably revolutionize a lot of learning.
Then we try to put in the West Coast offense; that took a lot of learning.
But I had a lot of learning to do in my life".
And to the four who said no, you have a lot of learning to do.
The troops at Justice, understandably, had a lot of learning to do".
"He's still got a lot of learning to do, like he said.
Ludwig does not simply clarify my doubts with English writing, it enlightens my writing with new possibilities
Simone Ivan Conte
Software Engineer at Adobe, UK