logged in user read and write page

Your Wix Data Query is wrong with the eq function.

.eq("iD". userId)

It should be like this.

.eq("_id", userId) 

See here for more info about system fields.
CMS (Formerly Content Manager): About Your Collection Fields | Help Center | Wix.com

Also, with your code, the page and the dataset onReady functions should be underneath your imports with the data query underneath that.

You need to make sure that the page and the dataset has fully loaded before you run your query on the dataset.