Usually when I working in a company.,

This needs to be combined with the next sentence.

For example, I was working at a company with many Korean customers.

Because I can talk to them while at work.

"Because" marks this as a subordinate clause, so this cannot stand alone as a sentence. It must be combined with the previous sentence.
"So that" is also better than "because," with the current phrasing. "Because" indicates motivation or cause here, but "I can talk to them while at work" refers more to the end result.

Now I am working at the Jockey cClub.

The customer is gambler onlyGamblers are the only customers.

Each time wWatching them betting on horses each time is kind of fun.

B(…) because by “betting,” you can see thea person's true color of a persons.

Again, this needs to be combined with the previous sentence.
The typical turn of phrase is "someone's true colors," not "the true color of someone."

I have never actually gambled before.

This describes something continuing from the past because you wrote "before," so the present perfect is needed.

Maybe it is time for me to start.

I want to feel that pleasure and angery too.

I will take the “nearby” advantageWhen I work at a company, I will usually take advantage of whatever is nearby.

Combining this sentence with the previous sentence sounds much better. "Usually when working in a company" is not a complete sentence on its own.

For example, I was working at a company with many Korean customers.

I started taking a Korean class.

Because I canof the class, I could talk to them while at work.

I would combine this with the last sentence: "I started taking a Korean class so that I could talk to the customers while at work."

Now I am working at a Jockey club.

The only customer iss are gambler onlys.

Each time wWatching them betting on horses is kind of fun.

Because by “betting” yYou can see the true color of a person. through their "betting."

Even a beautiful woman willmight scream loudly while gambling.

I have never actually gambled before.

I want to feel that pleasure and angery too.