Mountains such as Mt. Everest and Denali.I'd like to climb those mountains but l do not wanna lose body parts.How do good climbers do it?How do you minimize the risk?

You could start off by wearing warm clothes. Just make sure you always stay warm.

They stay warm. That is just about the only thing you can do.

Adequate clothing is a start, including protecting your face ( l frostbit my nose in Antarctica by not wearing a neck gaiter for 1/2 a day that covered my nose).

Adequate hydration is also key to avoiding frostbite. On Everest, supplemental oxygen also helps. Both help to keep your blood thinner and moving through your system.

Having your mates check your face, etc. is also key to helping to avoid it.

Develop ur basic rock climbing skills. Learn how to belay, tie in to the rope & practice the basic movements of climbing indoors at a gym or outdoors on rock.
Hire an instructor to show u the basics of ice climbing. This is an important step to take before u buy the gear. Guides have tools & crampons to try out before u make ur purchases.
Make sure u enjoy the wild sport of climbing ice before u buy all the gear. Some people learn that they would rather climb a warm dry rock in the sun.
Set aside at least three to four weekends each winter to travel to a major ice climbing destination.