this has been asked recently in the past week. please do a search in future.
1) read up on light to understand how to capture light rays, if they are not present vividly enough, yes, you need to underexpose. or you can lower the gamma in post process.
2) if you expose your sensor for UNREASONABLE amounts of time, yes, it may get damaged. but thousands and millions of people have been pointing their camera at the sun, and hardly anyone complains about getting their sensor damaged. so if you don't do something silly like a thirty-second exposure at the noon sun in its full glory and unshrouded in clouds at all.. you will be alright.