Bikes are not brain scanners. They are very basic combinations of mechanical components. They are not difficult to repair, but they do require a degree of skill and care and specialist tools.
Do not try to get by without the correct tool, you will do damage.
Do not use excessive force. By their very nature, bike components are lightweight and not desigened to withstand the operations of a gorilla on steroids. If a bit won't unscrew, there is a good reason for it. Find out what that reason is and attend to it.
If you don't understand how something works or fits, you will not be able to remove it, repair it and replace it. Research the problem first.
Accept that some things may be outside your skill level and let someone else do it and show you how for the next time.
Lecture over.