What happens if my bounty time expires?
I will lose this bounty points or I will take it back?
If I did a bounty but I had no answer, what's the next steps is suggested?
If you do not award your bounty within 7 days (plus the grace period), the highest voted answer created after the bounty started with at least 2 upvotes will be awarded half the bounty amount. If there's no answer meeting that criteria, the bounty is not awarded to anyone.
In any case, you will always give up the amount of reputation specified in the bounty, so if you start a bounty, be sure to follow up and award your bounty to the best answer!
If even after you imposed a bounty you get no answers, the most likely explanation is that no user currently active on the site knows the answer to your question. You can try asking it elsewhere, or wait a bit before assigning a bounty yet again (hoping that someone new and knowledgeable joins the community).