I have translated this from Czech (I do not speak the language but the email came from the email account from the lady who was PA before me).
I wouldn't usually think anything of it, however, I have watched some porn on my work phone 
Of which I was told to use as a personal phone if I wanted to.
Could there be any truth in this threat? What video does he mean? What does satisfied reaction mean, satisfied with what?
I'm really panicking.
Hi!
As you may have noticed, I have sent you an email from your account.
This means I have full access to your account.
I've been looking at you for months.
The fact is that you were infected with malicious software through the adult site you visited.
If you are not familiar with it, I'll explain.
Trojan Virus gives me full access and control over a computer or other device.
That means I can see everything on your screen and turn on the camera and microphone, but you do not know about it.
I also have access to all your contacts.
Why did not your antivirus detect malicious software?
Answer: I have a Trojan driver, I update his signatures every 4 hours so your antivirus is silent.
I made a video showing how you are satisfied in the left half of the screen and on the right half you see the video you watched.
With one click, I can send this video to all your emails and social networking contacts.
To prevent this, transfer € 255 to your bitcoin address (if you do not know how to do it, then write to Google: "Buy Bitcoin").
Bitcoin address: 18QJdD5yWJyjeAapaSZEPoCQE84ncxwLAq
Once the payment is received, I will delete the video and you will never hear me.
I'll give you 48 hours to pay.
I have a warning when reading this letter and the timer will work when you see this letter.
Filing complaints somewhere makes no sense because this email can not be tracked as my and Bitcoin addresses.
I'm not making any mistakes.
If I find you have a message or shared this message with someone else, the video will be immediately distributed.
Regards