If you were somehow able to be in the core of the Sun, you would indeed be subjected to extreme conditions that would lead to your destruction almost instantly. The core of the Sun reaches temperatures of around 15 million degrees Celsius (27 million degrees Fahrenheit) and has pressures that are millions of times greater than Earth's atmospheric pressure.
In these conditions, matter is in a plasma state, where atomic structures break down. Any human or typical object would vaporize in fractions of a second due to the intense heat and radiation. Additionally, the immense pressure would crush any known material. Thus, being in the Sun's core would be an instantaneous end under those fierce conditions.