In general SE sites are not well suited for tutoring and that goes for MSE as well.
SQL has been around long enough that many sites contain valuable info to get you out of the weeds. To be successful at that you need to know that the SQL dialect used by Data Explorer is Transact-SQL, aka the Microsoft SQL language used in its SQL Server product. This is also mentioned on the last page of the SEDE tutorial.
SQL questions can be on-topic on Stack Overflow combined with the SQL and SQL-Sever tag.
That said: When you have a partial query going that involves the schema of the Data Explorer and are stuck to extend it, run into an error or get unexpected results, feel free to post it here on MSE, tagged with support and data-explorer and one of the SEDE residents will take a look. Do include the query, any error(s) (as text! not as an image!) and what you're aiming for.
Alternatively you can check in SEDE chat if you're not sure if it is worth a question on its own.
Keep in mind SEDE is updated once a week on Sunday.
Use the awesome SEDE Tutorial written by the admirable Monica Cellio.
Say "Hi" in SEDE chat.