Some reports super slow to open,

The reports are all SQL. When I open the report, not run, it seems like it is running the report in the back, same when I switch between different tabs (Page1, Data, etc ) When I close it too. Not all reports just this one . What do you need from me?

This can be because report generator is trying to get list of fields from the database.
If sql is very slow it will take a while.
If you use parameters you can speed it up by using different default parameters
Or you can add some indexes to make SQL faster