I have a soar throat.

I have a sore sore throat.

I have a sore soar throat.

My co-worker had a cold and fever, but he came to the a office.

I gargle with a gargle.

I am sure what the meaning of 'a gargle' is :-)
Alternatives:
'I gargle with cold medicine'
'I gargle with mouthwash'
'I gargle with salt and water'

Take care of getting a cold in summer, my friends frineds.

Alternative:
'Be careful to avoid a cold in summer, my friends'

I Have a Sore Throat.

Titles are capitalized

I have a sore throat.

sore = painful
soar = kind of like flying

My coworker had a cold and fever, but he came to the office anyway.

I suppose that I caught a cold from him.

Take care not to get a cold in summer, my frineds.

My coworker had a cold and a fever, but he still came to the office.

I suspect that I got it from him.

I gargled with a mouthwash.

I hope that I will get better soon.....