"it's OK if you don't understand it now, it'll all make sense soon... "
You tend to come across this a lot when studying as a software engineer, you will be exposed to an overwhelming amount of esoteric knowledge, it is typical to become fearful and to question your ability to progress beyond that stage but from personal experience you'll eventually come to grasp those concepts.
There are so many free materials that help teach software engineering however so many people try to pick up the skill and falter along the way, this is because at the very beginning there's a lot of unfamiliar information to pick up. Eventually one will reach a level where problem-solving skills will be the determining factor responsible for your ability to provide solutions.
The first phase of learning software engineering is amassing knowledge, in this phase, you will consume voluminous materials and they will stretch the very limits of your mind, the second phase however is being able to make use of the knowledge you've acquired to solve unique challenges, algorithm challenges usually help with building problem-solving skills. You have to be patient enough to trust the process even when it's discouraging.