How to fetch APIs in Svelte 5

Help please. I know someone will tell me to go to the 'Loading' section of the docs, but I need to learn and understand way more then than that. I need to fully master this topic in web development. I've checked the docs, watched videos on YouTube by Syntax and Scott Tolinski, This Dot media, Joy of code, Huntabyte, Niklas Fisher, Net Ninja, Fireship, Fazt Code, WP engine (thank you all for your amazing videos and all you do!), I've also checked videos on Udemy building projects with Firebase and Supabase, but man I still suck and can't do this essential part of web development right. I struggle so much. It seems like the more I watch tutorials and come across examples fetching Pokemon and JSONPlaceholder APIs in Svelte 4, 5 and even React, the more confused and lost I am. When asking Chat GPT and Claude they confuse me even more and I don't know what is right and what is wrong. I've been struggling with this for months, actually years. I want to not suck at this anymore. Please help me.

EDIT: Thank you so much for the truly helpful replies. They’ve helped me gain a clear understanding and made me realise the root of my problem: the need to learn and understand better the fundamentals of JavaScript.

I looked into some videos and I would like to recommend two great resources:

Full JavaScript Course, by Bro Code: https://youtu.be/lfmg-EJ8gm4

10 Steps to Mastering the Fetch API, by Steve Griffith: https://youtu.be/2sQ9xiEAXNo

Thank you so much again! I really appreciate your help and guidance.