I was checked the investigation of afor the corona virus because one of my coworkers got infected with it.

All of employees ion the same floor were also checked, and they are waiting for the results.

Fortunately, I am negative of the virusmy results are negative.

Another common phrase that is used when talking about test results is:

Fortunately, the test came back negative.

I should try to hardbe careful to prevent it and be carefulgetting it.

I checked the investigationresults of amy corona virus test because one of my coworker got infected it.

I made these correction based on what follows, assuming this is what you meant.

All of employees ion the same floor checkedtested as well and they are waiting for the results.

Also consider "on my floor" instead of "on the same floor"

Fortunately, I am negativfree of the virus.

It could just be: "Fortunately, the result is negative."

I should try to hard to prevent it and be careful about it.