itch.io

Here is one that pretty much outlines almost all the basics that I use most often:

https://www.motoslave.net/sugarcube/2/docs/

and here's a reddit thread of other sites that are helpful:

https://www.reddit.com/r/twinegames/comments/au74yc/collection_of_tutorials_ive_...

hope this helps. otherwise there's many forum posts that are helpful in coding. good luck :]