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

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

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

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

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

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

Fortunately, I am negativfree of the virus. Fortunately, I am free of the virus.

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

Fortunately, I am negative of the virusmy results are negative. Fortunately, my 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 hard to prevent it and be careful about it. I should try hard to prevent it and be careful about it.

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