My friend asked me that how do youhow I've been copeing with the heat in this summer.

In Japanese, you wrote どうやって対処してる. To say this in English, we would use present perfect continuous (現在完了進行形) and say "I have been ___ing" or "I've been ___ing". You could also say, "My friend asked me how I cope with the heat," but the meaning and nuance is a little bit different from, "My friend asked me how I've been coping with the heat."

I try to avoid to gogoing outside or in a hot room as much as I can.

The other day, I tookmeasured the temperature outside, and it was 39,.1 degrees Celsius.

"Take/took the temperature" - At least in the US, as an American, I have only heard "take/took the temperature" used as an idiom (慣用句) for measuring the temperature of people and animals. Maybe it's different in other countries.
"Measure/measured the temperature" - again, at least in the US, we say "measure/measured the temperature" for rooms, the climate, stars, and things (not usually for people or animals in everyday contexts).

I saw thisThis is my first time seeing such a high temperature where I live for the first time.

I thought I shouldn't go outside during daytime except if I need to.

Even though the electric bill goes highup because I use the air-con all day long, but there's no other choice.

My friend asked me that how do youhow I cope with the heat in this summer heat.

Alternative: My friend asked me, "How do you cope with the summer heat?"

I said, "I try to stay inside where the air-con is on."

"AC" is a more common abbreviation for air conditioner

I try to avoid to gogoing outside or in a hot rooms as much as I can.

I saw thist's my first time seeing such a high temperature at where I live for the first time.

I thought I shouldn't go outside during the daytime except Iunless I really need to.

My friend asked me that , "how do you cope with the heat in this summer.?"

You could also say, "my friend asked me how I cope / am coping with the heat this summer."

I try to avoid to gogoing outside or in a hot room as much as I can.

The other day, I took the temperature outside, and it was 39,1 degrees Celsius.

I saw thisThis is the first time I have seen such a high temperature where I live for the first time.

The original sentence can be understood, but sounds very strange and a bit confusing.

I thought I shouldn'try not to go outside during daytime except when I need. to

Even though the electric bill goes high because I use the air-con all day long, but there's no other choice.

The Ssummer Hheat

My friend asked me that h "How do you cope with the heat in this summer."

I try to avoid to gogoing outside or into a hot room as much as I can.

The other day, I took the temperature outside, and it was 39,.1 degrees Celsius.

I saw thisThis is the first time I have seen such a high temperature where I live for the first time.

I thought I shouldn't go outside during daytime except I needwhen I have to.

Even though the electricity bill goes highup because I use the air-con all day long, but there's no other choice.