Yes, spaceflight is dangerous. It takes a huge amount of energy to send something into space, in a rocket that energy is stored as a tremendous amount of chemical energy in hundreds or thousands of tonnes of fuel. If it works properly then the energy is released in a controlled way and used to add the kinetic and potential energy need to put the spacecraft into orbit. If something goes wrong like it did with Challenger in 1986, the result is a terrible, unsurvivable explosion.
Just remember though, aeroplanes used to crash all the time, now ‘plane crashes are rare. As technology advances, space travel will become safer.
Yeah, there is always a risk. The more times you do something, the more chances there are for something to go wrong, but at the same time you get more knowledge and experience to know how to prevent disasters from happening. Eventually there will probably be a greater chance of astronauts being killed in a car crash on their commute to work than in a space disaster.