To get any meaning out of waiting tasks, you need to sample it at two occasions and compute the deltas. Else you have values accumulated since SQL Server last started, and it may be a hotchpotch of everything.
If you are on SQL 2016 enable Query Store, if you haven't done so. After a day or so, you can start to look at resource-consuming queries. There is a UI for it in SSMS, You find it under the node for the database.