Mac Mail junk settings and searches are not working

I think Mac's poorest performing application is Mail.

My first problem is mail from approved senders (in my Contacts) and Previous Recipients often get sent to junk (but sometimes get to the Inbox,too) even though my Settings say both should go to the Inbox. This seems to be common problem. Does anyone have a fix?

Second, I repeatedly mark certain messages as "junk," but other messages from the same sender just keep landing in Inbox. Fix?

My third problem is that searches of Mail often miss emails they should find. Again, does anyone have a fix?

Thank you.