Let's go to the basics. Looks logical to think that is OK to preserve your own life (self-preservation). Self-preservation is programmed into all animals on Earth, including humans. Undeniably, it is a basic instinct.
But when you think about it with some deep, it is really messed up, because, in same cases, you have to kill other beings in order to protect you own life. It is actually recommended, in some unambiguous cases, to destroy (using force if necessary) other forms of life in order to survive; security prevails in these cases.
In order to show you the moral complexity of self-preservation, we are going to use an example: Imagine that a group of people with large knives is approaching you. You have a gun. They're moving their knives in a dangerous manner. What you gonna do? They could be doing it just for a prank. Can you read their minds to know for sure that is just a prank? As weird as it may sound, there are real similar cases when it is just a prank, for example: https://www.bbc.com/news/technology-55982131
Even if we cannot give you a short perfect moral advice, here it is our try: We recommend to be peaceful as much as possible, and to use violence only when it is clear that there is a deathly (or really problematic) threat to you (if there is enough time to think about it) and it is completely necessary (there is no other normal way to avoid it).
