Over the past month (plus or minus a couple days), Erik Darling churned out dozens of posts to show how he uses different SQL Server Community Tools that are free and open source to troubleshoot SQL Server issues. You should read all of them. I did. (I also shamelessly copy/pasted this intro, plus the below, directly from his blog.)
Here’s the full list of posts:
SQL Server Community Tools: Capturing Blocking With sp_HumanEvents SQL Server Community Tools: Capturing Query Performance Problems With sp_HumanEvents SQL Server Community Tools: Capturing Which Queries Are Compiling With sp_HumanEvents SQL Server Community Tools: Capturing