You are being quite rude and snappy for somebody who asked for help and is being given great advice by people who are veterans in fish keeping.
You had no heater or thermometer so the unsuitable temperature isn't a surprise, this may have been having the largest impact on your Oscars behaviour.
You need to regularly check your water parameters, including ammonia, nitrites and nitrates and keep them as low as possible, Oscars are very messy fish. You will also need to make sure you have adequate filtration, nitrites and ammonia should be 0.
Your tank size isn't appropriate for the fish you are keeping, you will soon need to upgrade, Oscars are very fast growing.
I suggest in the future that you research and understand the needs of a pet before you decide to keep it.
You had no heater or thermometer so the unsuitable temperature isn't a surprise, this may have been having the largest impact on your Oscars behaviour.
You need to regularly check your water parameters, including ammonia, nitrites and nitrates and keep them as low as possible, Oscars are very messy fish. You will also need to make sure you have adequate filtration, nitrites and ammonia should be 0.
Your tank size isn't appropriate for the fish you are keeping, you will soon need to upgrade, Oscars are very fast growing.
I suggest in the future that you research and understand the needs of a pet before you decide to keep it.