Ideal CPU temperature while gaming

Hello, sorry if this has been posted a million times and seems repetitive, but I would like to hear your opinions on this matter.

What temperature is considered dangerous for your CPU when it is under stress (ex. gaming)? I've been searching and read that sustained temperature of 80Cs is dangerous for intel CPUs while 70Cs is fine.

I have an i7-4790. When gaming (CSGO), it can get up to 78C max, but usually stays around 55C-70C. Should I be worried and is it recommended to buy a new fan/cooler? I'm using a stock fan, by the way.

Thanks again for your time