On page About the ℹ️ Support category you are suggested to read 101 basics, but that page doesn’t exist anymore
Hey @Luuk welcome to the nextcloud community 
maybe you have misunderstood @LukasReschke who was suggesting you read the basics in the category tagged 101, which is not the clearest name we could have given that tag 
. that category 101 includes some documents explaining the basics in no particular order.
don’t be shy to ask if anything is unclear