Are these sentences natural? XI.V.MMXIX

Talk to him. He's adept at solving math.
or Talk to him. He's adept at math.?

Stop talking about video games. We are having an erudite discussion.

He was outburst when he overheard my bants about the headmaster.
or
When he overheard my bants about the headmaster. He outburst?

Back then I was down and out but I'm now full of prosperity.

The exam has been delayed by innumerable problems.

Thunder rumbles overhead.

We are commemorating 50 years of our company since 1970s (I suppose).

I was asking him for a phone number but he was boying it. (try hard to give sth - rare word. Got it from my mate)

I fell short when I failed the driving test.

She seemed very subdued. Is she alright?

A subdued lighting gave a feeling of solitary.