Today, I learned a proverbthe phrase "a bolt from the blue" which I think means a totally unexpected happening.

Proverbs are sayings that express some kind of wisdom or knowledge, "bolt from the blue" is just a descriptor

In Japan, a proverbthe phrase "青天の霹靂" that, which superficially means "a thunderbolt from the blue sky," means the same thing as "a bolt from the blue".

Putting the literal meaning in quotes and all the non-essential information between commas makes it easier to read

I googled it, and found their roots are completely different.

What's interesting it is that different personople in different cultures come up with the same ways to describe the same phenomenon.

Today, I learned about the proverb "a bolt from the blue", which I think means a totally unexpected happening.

このことわざについて学んだので、「about」の言葉が必要なんです。
さらに、ことわざの意味はみんなで考えが似ているね。だから、「I think」は必要ではないんです。

In Japan, athe proverb "青天の霹靂" that superfici, which literally means a thunderbolt from the blue sky means the same, has a similar meaning as "a bolt from the blue".

特別なことわざなので、「a」より「the」はもっと自然なんです。
文字通りのような意味を伝えたいか？そうなら、「literally」は「superficially」よりもっと明確なんだ。「superficially」は「表面的に」みたいな意味があるのです。

I googled it, and found their roots are completely different.

過去にググったので、「-ed」を動詞の終わりでかけるべきです。

What is interesting it is that different person ins from different cultures come up with the same way to describe the same phenomenon.

英語で、人々は文化や教科書などから情報を捉えられる。「from」という言葉はこの文脈にはとても大切なので、こう書けばいいよ。

Today, I learned a proverb "a bolt from the blue" which I think means asomething totally unexpected happening.

In Japan, there is a proverb "青天の霹靂" that superficiliterally means "a thunderbolt from the blue sky", which means the same as "a bolt from the blue".

'Literally' fits better than 'superficially' here, because you're describing what the phrase actually means (apart from its meaning as a phrase). Superficially would be used for something that lacks depth.

I googled it, and found that their roots are completely different.

What's interesting it is that different personople in different cultures come up with the same ways to describe the same phenomenon.

You'd use 'same ways' here instead of 'same way' because you're making a general statement. So you're referring to multiple 'ways', not just this particular example that you gave.