attacks – Recovery of a hacked phone

I have been hacked one way or another earlier this year and I am trying to find evidence to confirm the method. I have had conversations being listened to, and it is very likely that my Whatsapp messages have also been listened to.

I used the same wifi network as the attackers and they knew the details of my wifi network / router, including the password. I used an S6, unrooted. There was Lookout Security, however, I clicked on fake attachments and my phone had been left unlocked from time to time in the office.

No spyware has been found with conventional applications.

Is there a way to check if the phone or router contains evidence of piracy? The abusers had contact with people with good computer skills. Most computer scientists do not seem to know enough about it.